A Greens senator is a "team wrecker". Local members are "kept in the dark and fed on bullshit". Grassroots democracy in New South Wales is a "farce". And party founder Bob Brown should "f*** off".

These are just some of the stinging insults and allegations exchanged by figures in the Greens Party in a behind-the-scenes examination by Four Corners.

Key points: Bob Brown and other senior Greens have called on Senator Lee Rhiannon to retire

Bob Brown and other senior Greens have called on Senator Lee Rhiannon to retire Christine Milne says a staffer's 'joke' that Bob Brown should 'f*** off' reflects 'talk that goes on in some circles'

Christine Milne says a staffer's 'joke' that Bob Brown should 'f*** off' reflects 'talk that goes on in some circles' NSW branch claimed to be to be led by controlling group of people not directly elected by members

The sniping comes after a terrible winter for the Greens, where two senators were forced to resign because of constitutional bungles on dual citizenship and a third was locked out of voting in the federal party room for differences on schools funding policy.

Lee Rhiannon, who is the only elected Green from the country's most populous state, was in June temporarily suspended from voting in her party room after saying she was bound by the NSW party to adopt a different position on schools funding to leader Richard Di Natale and education spokeswoman Sarah Hanson-Young.

Lee Rhiannon was temporarily suspended from the party room over schools funding policy. ( ABC News: Four Corners )

This came while Senator Hanson-Young and Senator Di Natale were negotiating with the Federal Government over its so-called Gonski 2.0 legislation.

Senator Di Natale told Four Corners the party had all "collectively agreed on a statement of principles" and "we weren't aware one of our team had a fixed position and was campaigning against the position of the party room".

Senator Rhiannon pointed out the Greens' constitution fixed her to the position bound by the NSW Greens rather than a conscience vote with the rest of her federal party.

But party founder Bob Brown supported Senator Rhiannon's exclusion because she was a "team wrecker".

"I've had to take Lee aside when I was party leader and tell her that she was damaging the party through her actions," Dr Brown said.

"Her response always to me was to look me in the eye and say, 'Bob, I'm a team player'… Well, have a look. She's a team wrecker."

Dr Brown and other senior Greens have called on Senator Rhiannon to retire.

The former leader said: "I've been living with Lee for 30 years, but it's the end of Lee's reign. That end is nigh, and I look forward to the future."

Larissa Waters (right) is one of two senators forced to resign over citizenship bungles. ( ABC News: Four Corners )

Senator Rhiannon rejected Dr Brown's criticisms, and Hall Greenland, a co-founder of the Greens in NSW, said it was bound up in Dr Brown's bid for a more centralised, top-down party, which Senator Rhiannon and the NSW Greens oppose.

Speaking in a comedy debate held as part of the NSW Greens State Delegates' Council in Sydney, attended by Four Corners, Aesha Hussain, who was working in Greens MLC David Shoebridge's office, said Dr Brown should "f*** off".

Mr Shoebridge said nothing should be read into Ms Hussain's comment because it was a joke, but former leader Christine Milne was appalled by the comment.

"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," Ms Milne said.

NSW branch an 'exercise in puppetry'

The war with Senator Rhiannon and her allies in NSW has been brewing for decades and is bound up in a constitutional exemption for the NSW Greens, which allows the state party to bind its senator on policy decisions rather than allowing her to exercise a conscience vote, as all other senators do.

Senator Rhiannon said that made NSW a healthy grassroots democracy, but other Greens disputed that claim and said NSW had been destructive for the federal party.

Nick McKim said NSW local members were "kept in the dark and fed on bullshit". ( ABC News: Four Corners )

"What goes on in NSW is not an exercise in democracy — it's an exercise in puppetry," Tasmanian Senator Nick McKim said.

"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."

An internal survey commissioned by the NSW Greens, leaked to Four Corners, revealed only a third of members surveyed had attended the NSW State Delegate's Council, which makes policy, and fewer than half even knew what it was.

But Mr Greenland said members were well-informed and engaged in their party.

"The idea they are mushrooms and kept in some kind of closed, North Korean-type commune — that's manifestly ridiculous," Mr Greenland said.

Hall Greenland says members are well-informed and engaged in their party. ( ABC News: Four Corners )

Ms Milne said grassroots democracy in NSW was a "smokescreen" and a "farce".

"The members in NSW don't know the half of what goes on — they only know what a central committee allows them to know," she said.

Predictions of Greens' demise 'wishful thinking'

Senator Rhiannon remains impervious to the criticisms.

"Politics periodically gets messy," she said.

"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."

Senator Di Natale maintained the party could weather the current storm.

"People keep writing off the Greens — they do it time and time again," he said.

"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."