SARAH FERGUSON: Disunity is death - it's a truism of politics.

In recent times disunity destroyed the Rudd and Gillard Labor governments and it now threatens the Turnbull government.

But the Labor and Liberal parties are not alone.

As you'll see in tonight's program party in-fighting also threatens the viability of the Greens as a political force.

It's not long since the Greens reached their political peak, holding the balance of power in the senate after the 2010 federal election and putting their first MP into the lower house.

But since that time their share of the vote has been in decline… tensions that existed inside the party since its inception have boiled over into open warfare.

The Greens are traditionally a secretive organisation, resistant to outside scrutiny but our reporter Louise Milligan gained unprecedented access as some of the most senior Greens voiced their frustrations with stunning candour.

Her story begins in that extraordinary days in July when Scott Ludlum, the first of two high profile greens Senators, was forced to resign for holding dual citizenship.

LOUISE MILLIGAN: It's 9.30 on the New South Wales north coast and a politician is trying to catch a break.

The sun's shining, but it's been a horrible winter for Greens Leader Richard Di Natale.

RICHARD DI NATALE, LEADER, AUSTRALIAN GREENS: It's been a tough few weeks, no question about it.

We've had the loss of two incredibly honest, decent, hardworking people, two of the best politicians in Parliament.

But most importantly, two of the best people in Parliament.

And there's no sugar-coating that.

LOUISE MILLIGAN: Di Natale is rallying the troops ahead of a doorknock in Byron Bay.

RICHARD DI NATALE: We're bigger than one person, we're bigger than a Senator, we've lost two great people, we're going to get more good people to fill that spot and we're going to continue to grow, and we are going to grow because of the work of people like you volunteering for the things we are all fighting for.

So, let's get out there and start doorknocking! Good on you!

LOUISE MILLIGAN: It's tempting to wonder if the Greens have lost their way.

MAN: We haven't got a clue where we are or where we are going.

We're going the wrong way.

WOMAN: So, we're staring there, so that must be where the shopping centre is.

MAN: So, we're supposed to be going that way? Oh! Smile for the camera.

LOUISE MILLIGAN: Hardly anyone's home.

MAN: Next Suggestion?

WOMAN: We should door knock the beach.

WOMAN: Door knock the beach! Yeah!

LOUISE MILLIGAN: And those who are home don't want to talk.

At the Splendour in the Grass music festival, Richard Di Natale is among friends.

But the Greens vote is down from its high point in 2010.

Newspoll figures show that's a particular problem when it comes to young people: a key demographic for the Greens.

The youth vote fell three and a half per cent over the past two years.

Di Natale's hoping to re-gain momentum.

WOMAN: Do you wanna get a photo with Splendour in the grass?

RICHARD DI NATALE: What do you reckon?

WOMAN: Yeah, I do.

RICHARD DI NATALE: OK.

WOMAN: Richard, c'mon!

RICHARD DI NATALE: I can't compete with that!

RICHARD DI NATALE: how are ya!

BOY: what's your name?

RICHARD DI NATALE: Leader of the Greens. Richard, how are you, mate?

BOY: Leader of the Greens? In one year's time, I'll be voting for you.

RICHARD DI NATALE: One year?! Why don't you come over here and say in on camera? Come over here.

Why don't you put your drink down?

How old are you?

BOY: Seventeen.

RICHARD DI NATALE: Not voting yet?

BOY: No.

One year's time.

I'll be voting for the Greens.

RICHARD DI NATALE: Oh good, good, that's exactly what I wanted to hear.

Di Natale is constantly confronted with the news of the day, that two of his top performers have been forced to resign because of a citizenship bungle.

HOST: Next up, we have Greens leader and I presume Australian citizen, Richard Di Natale give him a round of applause for turning up.

How do you reassure your followers that you know what the fuck you're doing?

RICHARD DI NATALE: Oh, look, good people stuffed up, simple as that.

HOST: Yeah, but I heard you say that on the news the other night and it didn't really move me.

You say it's a stuff up, but it's really key, it means that they were never really senators.

It's a really big issue.

How do you make these people think that you are across your shit?

RICHARD DI NATALE: You do a thorough review and you fix it.

I've got to tell you, I reckon there might be a few other people who might be in the same boat.

Just quietly, I suspect there are a few other politicians on all sides.

ANTHONY ALBANESE, ALP: Come on Richard, that's disingenuous to be fair.

People sign a form saying that they're citizens of Australia and not of another country.

You can't just slur the whole parliament and say, 'I reckon there are others.'

RICHARD DI NATALE: But Albo, it's actually about knowing it.

HOST: I'm Tasmanian, does that count?

RICHARD DI NATALE, LEADER, AUSTRALIAN GREENS: People keep writing off the Greens, they do it time and time again.

After every election, I hear the same story.

When Bob Brown resigned as leader, that was the death of the Greens.

When Christine Milne left, the same again.

There's a bit of wishful thinking going on here.

We're a strong and growing political force.

I'm very confident and optimistic about our future.

LOUISE MILLIGAN: There's this perception of the Greens that it's everyone sitting around, holding hands and singing Kumbaya, is that a reality?

IAN COHEN, FORMER NSW GREENS MP: No.

Not in NSW.

There are a lot of people pushing their agenda.

The Greens have more to deal with than the loss of two Senators.

Three weeks before the resignations, the party has gone into open warfare.

At the centre of it is Lee Rhiannon, Senator for NSW.

LEE RHIANNON: Although the last couple of weeks obviously has been quite a shake up, it doesn't mean we can't continue to work together in a very productive way.

Politics periodically gets messy.

And I think if you think the answer is to make it all neat and tidy - I think you hear these days, make it professional, make it efficient, is missing the point about our progressive politics.

LOUISE MILLIGAN: Lee Rhiannon has become a major thorn in Richard Di Natale's side, but at a National Union of Students conference in Brisbane, she's hugely popular.

Rhiannon has been suspended from voting in the Greens federal party room for going against the Greens' decision to negotiate with the Government on its schools funding package.

STUDENT: We've seen Lee Rhiannon, who is sitting in the middle here, she is excluded from all decision making within the party room.

That is a motion, Larissa, that you put your name to.

It's a motion that you voted for.

LOUISE MILLIGAN: It's an uncomfortable morning for Larissa Waters who's sitting next to Lee Rhiannon.

She's one of eight members of the Greens team who excluded Lee Rhiannon from the party room.

STUDENT: The National Union of Students stands in solidarity with Senator Lee Rhiannon.

Against the Right-wing attack on her being carried out by the leadership of the Greens.

NUS fights for and wholeheartedly supports resistance to the war on students, workers and the oppressed.

All those for the motion? Motion is carried.

STUDENTS: Oh, Lee Rhiannon! Oh, Lee Rhiannon! Oh Lee Rhiannon!

A handful of Greens students disagree with the motion supporting Senator Rhiannon.

STUDENT: We think it's absolutely shameful of them to cast a bad light on the Australian Greens Party, to state that the leadership of the Greens is right wing is just not correct at all.

LOUISE MILLIGAN: But the support for the federal party is quickly drowned out by the cheer squad for Lee Rhiannon.

STUDENTS: Oh, Lee Rhiannon! Oh, Lee Rhiannon! Oh Lee Rhiannon!

LOUISE MILLIGAN: While the students loudly support her, for Lee Rhiannon's federal colleagues, her decision to break ranks on schools funding is the last straw.

RICHARD DI NATALE, LEADER, AUSTRALIAN GREENS: What was clear was we had all collectively agreed on a statement of principles and we were negotiating to try and get the best possible outcome we could for kids in public schools.

What actually happened was that we weren't aware that one of our team had a fixed position and was campaigning against the position of the party room.

BOB BROWN, FOUNDER, AUSTRALIAN GREENS: Contrary to the Australian Greens grassroots members' conference agreement for this process, Lee went out and pulled the rug out from under it.

LEE RHIANNON: I think some even said that I had destroyed the negotiations with the Turnbull government.

Now, that really is ridiculous.

One person can't do that.

LOUISE MILLIGAN: Years of private animus exploded into the public domain.

LEE RHIANNON: I have been disappointed in Richard's leadership but you need to lead for everybody and it is not just me locked out of the party room, the Greens NSW members no longer have a voice in the party room.

RICHARD DI NATALE: Well, Senator Rhiannon was disappointed in Bob Brown's leadership.

She was disappointed in Christine Milne's leadership.

It's not a surprise that she's disappointed in mine.

In fact, I don't think she believes in leaders at the state or federal level at all.

CHRISTINE MILNE: She was disappointed in Bob's leadership, she was disappointed in my leadership, she's disappointed in Richard's leadership.

The fact is Lee doesn't support leadership.

BOB BROWN: I support Richard and his nine against this destructive behaviour by Lee Rhiannon.

And the way they've handled and tried to get a better outcome and taken on Lee.

You can argue whether it was the right prescription or not.

It's a courageous thing to do in politics.

It's necessary.

It's something they'll all want to have over and behind them, but it was high time, it was coming.

The gloves in the Greens Party are now well and truly off.

BOB BROWN: I've had to take Lee aside when I was party leader and tell her that she was damaging the party through her actions.

And her response always to me was to look me in the eye and say 'Bob, I'm a team player'.

LOUISE MILLIGAN: Is she a team player?

BOB BROWN: Well, have a look.

She's a team wrecker.

The bitter divisions between NSW and the rest of the party go back to the very origins of the Greens.

The Tasmanians were the world's first Greens Party - formed in 1972 after the flooding of Lake Pedder to create a hydroelectric dam.

Next came the campaign to save Tasmania's Franklin River, led by a young Bob Brown.

BOB BROWN ARCHIVE

LOUISE MILLIGAN: In NSW, a distinctly leftist inner-city movement had sprung up - inspired in part by Sydney's union green bans to save heritage areas from developers.

A young Lee Rhiannon was part of that, she'd cut her activist teeth protesting against apartheid.

LEE RHIANNON: Mum and Dad were in the Communist Party - what was then called the "Known Communist Party" which was code in the Cold War for people who worked in the Communist Party.

HALL GREENLAND, CO-FOUNDER, NSW GREENS: Some of us had been expelled or disillusioned with the Labor party and Communist Party and far-left groups and so on.

We'd been involved in urban environmental struggles and we'd been involved in saving forests, northern and southern NSW, and we just thought it was the time for the Greens.

LOUSIE MILLIGAN: But the NSW Greens wanted to remain autonomous within the federated party led by Bob Brown.

HALL GREENLAND: Bob was a much more centralising, top down, kind of political operator and we were much more grassroots.

We're much more radical, if you like, there were a lot more socialists and anarchists and so on involved in the formation of the Greens in NSW.

CHRISTINE MILNE: They said they would not join the Australian Greens unless they could regard their elected members as delegates to be directed by a committee in NSW and they had no ability of their own to make decisions.

That was really hard-fought and it was apparent that there would be NO Australian Greens unless NSW was given an exemption and therein lies the problem that has been with us for more than 25 years.

BOB BROWN: It's not just the members who have been cheated there, it's the voters.

Voters like to have an MP they like the look of getting in and being true to her or his electoral platform and performance.

The NSW Greens don't trust that or the voters.

The Greens bleak winter continues.

In Sydney, the NSW Greens are meeting to decide how to respond to their Senator's suspension from the national party room.

The meeting's known as State Delegates' Council and it's the biggest the Greens in NSW have ever had.

LEE RHIANNON: The feedback I'm getting, people are very keen for the party room to finish up, remove that decision that they made, that I shouldn't be in the party room.

DAVID SHOEBRIDGE: Lee's our NSW Senator.

The Senator for the biggest state in the country.

And she absolutely needs to be a part of that party room.

LOUISE MILLIGAN: Party HQ has sent delegates an email warning them not to engage with journalists.

It recommends "smiling and walking calmly" and says only authorised spokespeople are allowed to speak on behalf of the party.

The warning appears to have been dutifully heeded.

LOUISE MILLIGAN: Hi, we're just from Four Corners, we're just wondering about how you're feeling about the tensions in the party at the moment?

WOMEN: No comment.

No comment.

No tensions.

LOUISE MILLIGAN: No tensions? A Senator being kicked out of the federal party room's not tensions?

WOMAN: Thank you.

Have a good morning.

WOMAN: Why are you filming us?

LOUISE MILLIGAN: We're here to cover the State Delegates Council.

The reason why is you put the sign up there and we were interested.

WOMAN: I neither confirm nor deny that.

LOUISE MILLIGAN: Just because you put the sign up there.

And we wondered what your position was on Lee Rhiannon's…

WOMAN: You want to speak to the NSW Greens.

I do not speak on behalf of them.

WOMAN: Hey.

I'm photogenic.

LOUISE MILLIGAN: We'd like to talk to you, you were up there putting the sign up.

WOMAN: Stop talking.

Just ignore them.

Let's go take our photo.

LOUISE MILLIGAN: We're really interested, because on your sign up there, you talk about a grassroots party, this is a grassroots party.

So, you're part of the grassroots.

WOMAN: Our spokespeople are democratically elected.

And that's the co-convenors of the Greens NSW are our spokespeople.

I'd encourage you to talk to them.

LOUISE MILLIGAN: But this is a grassroots party and you don't seem to want to talk to us.

WOMAN: You can get my face it in, but no audio.

Cut the audio out.

LOUISE MILLIGAN: What do you think about Senator Lee Rhiannon's position?

WOMAN: I don't know.

I don't have thoughts!

LOUISE MILLIGAN: Former Greens Leader, Christine Milne, is venting years of frustration at her NSW colleagues.

CHRISTINE MILNE: Grassroots democracy in NSW is a smokescreen.

The members in NSW don't know the half of what goes on.

They only know what a central committee allows them to know.

As the leader of the Australian Greens, I wasn't able to directly contact the members in NSW.

The central committee in NSW would decide whether it was appropriate that I contact the members, when I could contact them, and they also exercised the right to censor what I had to say.

LOUISE MILLIGAN: There are also deep concerns about a drift to the hard left in the NSW Greens through a group called Left Renewal.

CHRIS HARRIS, FORMER TREASURER, NSW GREENS: One of the agenda items for Left Renewal is to dismantle the capitalist system in Australia.

Well, I don't support that, and I don't' think a lot of people who are supporters of the Greens and are members of the Greens would support that either.

LOUISE MILLIGAN: Good luck with that.

CHRIS HARRIS: Yeah, good luck with that.

Exactly.

The NSW Greens champion consensus - meaning 75 per cent of delegates must agree to a decision for a vote to be carried.

But that means that a quarter of the delegates can, if they organise effectively, block the majority.

Lee Rhiannon's faction is accused of regularly using this tactic.

JUSTIN FIELD, NSW GREENS MLC: You'll have a few people block just everything as a matter of

course.

And so, when small groups, really cohesive groups, just block through the course of a debate or discussion, at the end of the day, fair-minded people who genuinely want to bring goodwill to the room and participate, they just throw their hands up and they just let things go through.

Consensus is claimed.

I always call it consensus by exasperation.

DAVID SHOEBRIDGE, NSW GREENS MLC: Does it take time? Yeah.

Does it take commitment? Yeah.

Do you have to turn up to a bunch of meetings? Yes, you do.

But it's a system that works and it's a system where we've looked at what the other parties do and we say we do not want that.

NICK MCKIM, GREENS SENATOR FOR TASMANIA: What goes on in NSW is not an exercise in democracy, it's an exercise in puppetry.

And the puppeteers are a small cabal of people who are not directly elected by the members, who believe in top-down command and control, they treat their members like mushrooms - they keep them in the dark and they feed them on bullshit.

HALL GREENLAND: No, we are not.

People read! The Fairfax press, they watch the ABC, they even read the Murdoch papers.

They know what is going on! I mean, they are politically engaged, active people.

The idea that they are mushrooms and kept in some kind of closed, North Korean-type commune, I mean that's, manifestly ridiculous.

LOUISE MILLIGAN: Member of the NSW Upper House, Jeremy Buckingham, has been pushing to reform a party structure he sees as deeply undemocratic.

JEREMY BUCKINGHAM, NSW GREENS MLC: At every stage where I've tried to democratise NSW, I've been blocked by Lee Rhiannon and her faction.

I've pushed for membership plebiscites on key policy issues.

I've pushed for direct election of office bearers.

I've pushed to have our committees and State Delegates Conference opened up through online webcasts, so more people can participate.

But, at every stage, I've been blocked by Lee.

LOUISE MILLIGAN: When you say, 'blocked by Lee, how do you know, 'blocked by Lee'?

JEREMY BUCKINGHAM, NSW GREENS MLC: What I see, again and again is Lee and her factional allies, blocking these moves at State Conference, blocking them in key committees.

They get up, they say, 'no, no, no'.

LEE RHIANNON: It is significant that those proposals have been put to the state meeting a number of times, and they have been rejected.

They've been rejected because of people's commitment, that we work as a collective organisation, and that is really the success of the Greens, is coming together, learning from each other, and building on that work.

CHRISTINE MILNE: It's a way of making sure that the members in NSW are never fully informed or only get the information that a certain group of people want them to have.

That's why this whole thing about grassroots democracy is such a farce.

LOUISE MILLIGAN: Former City of Sydney Councillor Chris Harris quit his position as the NSW party's Treasurer in disgust late last year.

He says his local group was opposed to Lee Rhiannon's split with the Greens' leadership on schools funding reform.

CHRIS HARRIS: As a member of the Greens, I'm disappointed.

I don't think it was a proper, it certainly wasn't a grassroots decision.

There was plenty of time for the party or the Senator in this case to consult with the party and to ask the local groups what they thought about what she was proposing.

LOUISE MILLIGAN: And that didn't happen?

CHRIS HARRIS: Did not happen.

LOUISE MILLIGAN: The decision that Lee Rhiannon would adopt a different policy from the rest of the Party, was made by a committee of six people.

LEE RHIANNON: They're a group of people that I discuss tactics with and issues arising through my parliamentary work.

We had had a number of discussions about this legislation.

Public education is a big thing for the Greens and determined that we should stick with policy.

LOUISE MILLIGAN: The parliamentary liaison committee, did it consult the grassroots?

LEE RHIANNON: Well, it's been consistent with the grassroots position.

The grassroots of the party have adopted a policy of the full Gonski.

LOUISE MILLIGAN: We've spoken to a number of Greens members who say their local branch wasn't consulted at all, and in fact, had they been consulted, they would have said that they didn't agree.

LEE RHIANNON: Well, if they didn't agree, that would be going against policy, and that's something that's written into our constitution is to follow policy.

LOUISE MILLIGAN: But I thought this was a grassroots decision.

LEE RHIANNON: It is a grassroots decision, but what we're bound by, is, ah, policy.

LOUISE MILLIGAN: Back at the State Delegates Council, after nine hours of deliberations about the federal party room's decision, the NSW Greens come outside with an affirmation of support for their Senator.

WOMAN: We also as the Greens NSW requested that our Senator be fully reinstated without restriction to the federal party room for all meetings, decisions and operations.

We also request that the federal party retract its proposal and offers an apology to Lee Rhiannon.

LOUISE MILLIGAN: Later on, they will retract the demand for an apology - saying it was just part of a draft statement.

They want Four Corners to remove it from the record.

We politely decline.

Later that night, the NSW Greens gather for a shin-dig.

They're staging a comedy debate.

WOMAN: Time for our next speaker, Lee Rhiannon! Just as good, Aesha!

AESHA HUSSAIN, NSW GREENS: I'm Aesha.

Not as good as Lee Rhiannon, but I'm sure you guys can live with the disappointment.

LOUISE MILLIGAN: The topic's about whether people over 50 should be allowed to participate in politics.

AESHA HUSSAIN: If you had only under fifties voting, we would have same sex marriage, we wouldn't be locking up refugees and we would have some serious action on climate change.

MAN: We'd all have legal DRUGS!

AESHA HUSSAIN: We'd all have legal drugs! How much better would this be if you all had some drugs right now? This would be hilarious.

Like, I know I'm really funny, but imagine me ten times funnier!

LOUISE MILLIGAN: It may have been a comedy debate, but they weren't pulling their punches when talking about Greens party founder, Bob Brown.

AESHA HUSSAIN: So, I'm just going to start reiterating the points of my team-mates.

The first one I've got is 'Bob Brown should fuck off because he's over 50'.

Couldn't agree more.

That was simple.

This speaker Aesha Hussain, has been working for member of the NSW Upper House, David Shoebridge, a long-time factional supporter of Lee Rhiannon.

LOUISE MILLIGAN: I was surprised at the level of animus in that room towards Bob Brown.

DAVID SHOEBRIDGE: I think when you're talking comedy, you're talking comedy.

LOUISE MILLIGAN: Isn't all the best comedy based on a bit of truth? Isn't that what makes it funny?

DAVID SHOEBRIDGE: I'm a politician, I'm not a theatre critic.

CHRISTINE MILNE: A joke is a way of trying to excuse it, but let me tell you, I know that behind the so-called jokes, that kind of talk does go on in some of those circles.

BOB BROWN: I've got broad shoulders, I wouldn't use the language or the hectoring or the bullying that they use.

I just don't think that's good human behaviour.

But I've always lived with that and will into the future and will see them out.

LOUISE MILLIGAN: But it might not be that easy.

The anti-Bob Brown sentiment in these circles runs deep.

TOM RAUE, NSW GREENS: Well my issue with Bob Brown is that he, for a long time, has been waging this crusade against the New South Wales Greens.

He thinks it's somehow more democratic for an MP to exercise a conscience vote rather than members deciding policy and the MP being a delegate of those members, which is what Lee does.

And Bob clearly has a problem with that.

I think he just needs to butt out and mind his own business.

LOUISE MILLIGAN: This antagonism towards Bob Brown goes back more than a decade, according to NSW Greens Upper House MP, Jeremy Buckingham.

JEREMY BUCKINGHAM: At the national conference, I was pulled aside by Lee Rhiannon's partner, Geoff Ash, who demanded that I go into the National Conference and attack Bob Brown and call him a megalomaniac.

They wanted me to say that he should not be the parliamentary leader because he was a megalomaniac, he would accrue too much power and they would never get rid of him.

I said to Geoff, I said to Lee 'I'm not going to do it'.

I left the conference.

LOUISE MILLIGAN: What happened to you after that?

JEREMY BUCKINGHAM: Well, after that, I said no, and I was put in the freezer.

My roles were cut.

Access was cut.

The phone calls were cut.

I was put in the freezer.

LEE RHIANNON: So often, fabrications, misinformation… I have not talked to anyone like that.

It's not my style of work.

I'm deeply committed to being inclusive and so is my partner.

LOUISE MILLIGAN: Her partner Geoff Ash told Four Corners while there was no love lost between him and Bob Brown, Buckingham's claim was "nonsense".

LEE RHIANNON: And Jeremy is the one who is known for gross misinformation.

LOUISE MILLIGAN: Can you give me some examples of this gross misinformation?

LEE RHIANNON: I'm not going to go down that line, but there is a long history here, and to say that about myself, and it does make me sad to bring my family into it.

LOUISE MILLIGAN: Ian Cohen is a veteran of the Greens public and private battles.

IAN COHEN: Chained to trees, rode nuclear warships, worked on the theatre of the environment.

Colourful, hopefully clever, sometimes disastrous actions that would attract the media to the issue.

But Cohen says the sniping from his fellow Greens during his years in the NSW Upper House pushed

him to the brink.

IAN COHEN: We had quite a number of people who were constantly working towards their own particular goals, which from my perspective, was mainly building up power within the confines of the party.

It was difficult, I was constantly at war.

And I went through times of really acute depression because they were really pushing me all the way along the line and often actively working against me.

LOUISE MILLIGAN: For Justin Field, who's now in the State's Upper House, things got so poisonous he was blocked from joining Lee Rhiannon's local branch after a disagreement about political donations with her and her ally John Kaye, who has since died of cancer.

JUSTIN FIELD: Without even being told the group was going to meet to discuss it, I was told my membership had been refused.

I had just been a candidate for the party in the Upper House in the 2015 state election.

I was very soon after preselected to be an MP.

But the Waverley Greens apparently by consensus decided I was not trustworthy to join that local group.

LOUISE MILLIGAN: Why did the Waverley Greens decide that Justin Field wasn't allowed to be a member?

LEE RHAINNON: That decision was taken after a discussion about his actions and the way he has treated people, and particularly in that case, myself and the now-deceased John Kaye.

LOUISE MILLIGAN: You keep talking about grassroots democracy.

Surely someone who is now a member of the NSW parliament, so Greens members and Greens voters have decided he's someone worth representing them.

Surely that's someone who is actually worthy of being a member of being a member of a local grassroots Greens group?

LEE RHAINNON: Not necessarily! Everybody in Parliament doesn't deserve to be there.

That's something you learn pretty quickly when you sit in Parliament.

DAVID SHOEBRIDGE: Do people have disagreements in a political party? Well, gee, pull down the banners, hold the front page.

People in a political party have differences.

We're not saints as Greens MPs and no-one should think we are.

We're a bunch of flawed individuals trying to do the best we can in a totally crooked political system that we've inherited from the likes of the Labor Party and the Liberal Party and we want to make it different.

That is super challenging.

IAN COHEN: I believe that we haven't been well-led in recent times in NSW.

I think that it is something that we need to talk about, talk about it publicly and not hide behind some cloak of secrecy.

LOUISE MILLIGAN: By mid-July, things are starting to look up for the Greens.

Lee Rhiannon's been allowed back into the party room.

But another crisis is about to grip the Greens.

So, we're at this Bob Brown event here at Federation Square in Melbourne.

And suddenly, just as everyone's talking about Lee Rhiannon, the focus shifts.

This time, to WA Senator, Scott Ludlam.

He's resigned.

Turns out, he's got dual citizenship with New Zealand.

And the constitution doesn't allow it.

He says it's only just been brought to his attention.

LOUISE MILLIGAN: We just wanted to ask you about the news today of Scott Ludlam resigning?

BOB BROWN, FORMER LEADER, AUSTRALIAN GREENS: Ah yes, what a pity.

It's a big loss to the Senate.

Not just to the Greens, but for everybody.

Because he's been such a great asset.

Greens at the event like Victorian Senator Janet Rice are rattled to lose Di Natale's co-deputy leader.

JANET RICE, GREENS SENATOR FOR VICTORIA: Gutted, basically.

He stuffed up.

Sorry, and it's just going to be such a loss.

Huge loss.

SCOTT LUDLAM, FORMER GREENS SENATOR FOR WA: It's been an incredible run, and I've enjoyed every minute of it.

And I think probably, when it all goes quiet, or when they ring the bells on my colleagues in August and I'm not there, that's when it's really going to settle in.

Alright thank you so much all, see you in the next life.

It only gets worse four days later when Di Natale's other deputy, Larissa Waters, has to resign for the

same reason.

LARISSA WATERS, FORMER GREENS SENATOR FOR QLD: It seems that the law was changed a week after I was born and in fact I should have actively renounced Canadian citizenship.

I'll now obviously do that.

I just want to apologise to my party and to all of the wonderful Queenslanders that I've been so

proud to represent.

It's been a real honour to speak for them and to stand up for things that I'm really passionate for.

RICHARD DI NATALE: To lose Scott Ludlam and Larissa Waters is a big blow, but I'm confident that the party will come together, that we're going to make sure it doesn't happen again, review the way we vet our candidates, and just to ensure that we continue giving all of those members and supporters that have fought so long for the Greens confidence to know that it won't happen again.

CHRISTINE MILNE: They were both fantastic Senators and I hope that we won't lose them from Australian politics in the longer term.

It again highlights why you need a really efficient, well-resourced national organisation.

The other parties have that.

While her leader is travelling the country, trying to hold his party together, Lee Rhiannon has flown to the Middle East and is crossing into Palestine.

LEE RHIANNON: When you see it like that you can see why they call it an apartheid wall.

What you see when you arrive in this country is apartheid.

From the Westbank to Gaza, people are treated like second class citizens.

Their human rights are ignored or abused.

LOUISE MILLIGAN: And she's still lobbing political grenades at her party: reviving a campaign to boycott Israeli businesses in Australia which seen a backlash against the Greens in the past.

LEE RHIANNON: There is value in this campaign, and it's a reminder why people like ourselves in

Australia and many around the world, it's time to reassess this form of struggle, because there is very clear examples of the value it brings to solidarity and the results is can achieve.

LOUISE MILLIGAN: Her leader disagrees.

RICHARD Di NATALE: It's not something that the Australian Greens have ever supported.

It's not something that I support.

LOUISE MILLIGAN: It's these sorts of clashes with the federal party that have prompted the Greens elders to tell Four Corners it's time for Senator Lee Rhiannon to go.

BOB BROWN: Oh, well, you know, I've been living with Lee for 30 years, but its' the end of Lee's reign.

That end is nigh, and I look forward to the future.

CHRISTINE MILNE: I think that the current behaviour in New South Wales is actually the death throes of that small cabal.

I say that because Lee has burnt her bridges with her parliamentary colleagues, she's burned her bridges with the Australian Greens.

LOUISE MILLIGAN: Will you run for Senate preselection at the next election?

LEE RHIANNON: Yes, I'm on track.

LOUISE MILLIGAN: You don't think it's time to sort of hand on the baton to the next generation?

LEE RHIANNON: Well, that will certainly happen at some time. At the moment, there's more work to do.

LOUISE MILLIGAN: Lee Rhiannon is back and she's not going anywhere.

She's energised and unstoppable.

She models her campaign on British Labour leader, Jeremy Corbyn.

LEE RHIANNON: Here is a Labor leader, campaigning on free higher education, re-nationalising the

railways, democratising the workplace, speaking about socialism, inspiring people.

Totally just demolishing all those people who say, 'he's a silly old bloke.

He's going to ruin Labor.

Unelectable.

Labour may not even exist if he stays in the job.

The biggest swing to Labour since the Second World War.

Now, this is something that can inspire us.

LOUISE MILLIGAN: Do you think that Lee Rhiannon's the Jeremy Corbin or Bernie Sanders of the New South Wales Party?

HALL GREENLAND: I think so, yeah, and I think a lot of other people think it.

She's a genuine fighter and principled person and she's been quite effective in her way.

BOB BROWN: She's as much Jeremy Corbyn as I am Santa Claus.

Lee's just jumped onto that quite falsely.

Jeremy Corbyn and Bernie Sanders would be appalled at the way in which Lee has cut out her membership and policy basis to overrule that of let the members decide, and let the grassroots decide.

It's a convenient shorthand for Lee to claim she's something that she absolutely isn't.

LOUISE MILLIGAN: The Greens bitter winter is not over yet.

They remain deeply divided.

Their popular support has fallen and Richard Di Natale has lost two key allies.

The pundits are tipping that at the next election the Greens face losing a further three Senators.

LOUISE MILLIGAN: Are you absolutely certain that you are safe as leader of the Australian Greens?

RICHARD DI NATALE, LEADER, AUSTRALIAN GREENS: Absolutely.

I think the things that have been discussed, publicly, aren't helpful.

But, in the end, it is what it is and as leader of the party, my job is to make sure that you show leadership not just when times are easy but also when times are tougher.

And sometimes adversity has a way of bringing people together.

NICK MCKIM, GREENS SENATOR FOR TASMANIA: We're a relatively young political party, and we've got some growing pains to go through, and we're going through some now, but we will come out of this stronger.

We'll come out of it more professional.

LOUISE MILLIGAN: Is this the Greens Killing Season?

NICK McKIM, GREENS SENATOR FOR TASMANIA: No, I wouldn't put it like that.

SARAH FERGUSON: A glorious summer for the Greens seems a long way off - in the meantime Senator Lee Rhiannon will face a challenge to her pre selection in October. Next week is Australia in a housing bubble and what happens if it bursts?