Bob Brown has announced he is quitting politics, after a career which saw him grow the Greens party from nothing to become the third force in the Senate.

The 67-year-old called a snap meeting of his party room colleagues this morning to tell them it was time for him to go after 16 years in the Parliament.

He told them he was quitting as party leader and would also leave the Senate by June.

"I am 67. I am aware that one should always make room for renewal in politics. A democracy is the healthier for the turnover of the depth of talent there is in its community," he told reporters at a press conference in Canberra.

Senator Brown leaves the Greens in historically high numbers in the parliament, with a total if 10 members in the House of Representatives and Senate.

The party wasted little time in elevating Senator Brown's deputy Christine Milne to the leadership, with Lower House MP Adam Bandt later voted in as deputy.

Here's how the story unfolded on our live blog:

1:34pm: PM Julia Gillard has issued a statement thanking Bob Brown for his: "Remarkable contribution to state and federal politics over the last three decades."

1:27pm: Tasmanian state Greens leader Nick McKim will hold a press conference at 3:00pm. Bob Brown says the Tasmanian party leader has already ruled out a move to Canberra.

1:26pm: You can read Bob Brown's resignation letter here.

1:04pm: On ABC News 24, political correspondent Lyndal Curtis says it "seemed to me during that media conference that it did seem that he had a weight lifted from his shoulders.



"He looked a little relaxed. He kind of had been showing the stresses and strains of it all over the last year or so."

1:03pm: You can watch the video of Bob Brown's statements to the press conference here.

1:00pm: Bob Brown's resignation ends a trailblazing career in federal politics which saw him become Australia's first openly gay member of Parliament. Read more here.

12:55pm: Watch video of Christine Milne at this lunchtime's press conference.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 5 minutes 8 seconds 5 m New Greens leader Christine Milne pays tribute to Bob Brown

12:40pm: Press conference over. The key points:

No change in the agreement with the Government.

in the agreement with the Government. Christine Milne to extend an olive branch to the bush while taking the fight to "rapacious" miners.

Christine Milne to while taking the fight to "rapacious" miners. Bob Brown says he's confident the party will flourish in his absence .

Bob Brown says . "The Greens are on trajectory to become a future government. Our job isn't to make the so-and-sos honest - it's to replace them," Brown predicted.

12:37pm: Bob Brown rejects a suggestion that the Greens could "go the way of the Democrats" in his absence: "No, there's a difference, which is very clear, in the vision that the Greens are putting forward and our ambition to replace, not be a check on, other people in this Parliament.

"In fact - this is my honest feeling - that predominant leadership, and I've been a strong leader, can suppress the talents of the people that you work with. And this is a very talented bunch. So quite the contrary."

12:35pm: Life after politics:

@annabelcrabb: [Bob Brown's partner] Paul says he is "looking forward to testing Bob's athleticism on the mountains of Tasmania" and getting him to do the washing-up more.

12:30pm: There will be a party room meeting later today to decide who gets to be Greens deputy leader. And meanwhile, Brown compares today's fight against big business to the fight against "vested interest" of slavery in the 19th century. Says inspired by visit by tales of struggle on visit to old slave port in Senegal earlier this month. "The world needs Florence Nightingales and [William] Wilberforces," he says.

12:27pm: Brown says "we're in a very big downturn where the mining corporations - look at those ads in today's paper - can't be matched by non-government organisations, and we're seeing a roll over of community which is purchased democracy, a la America."

12:25pm: So, who gets Bob Brown's Senate seat?

@annabelcrabb: "Bob Brown says he has spoken with Tassie Greens leader Nick McKim and McKim is not interested in the Senate seat."

12:23pm: Christine Milne is giving it to the miners. "What we're seeing is actually a bigger play about the old vested interests of the resource-based economy trying to hold on to their vested interests for as long as they possibly can, and the proponents of the new economy being lukewarm and not as out there as they might have been in proposing the benefits of the new economy.

"It is something Machiavelli recognised in the 15th century, and it is being played out in this Parliament."

12:22pm: From @annabelcrabb: "Milne says that business in Australia is now "not heterogeneous"... Says she intends to distinguish between businesses who get the new economy and those who don't."

12:19pm: Christine Milne says: "I think the Greens and the bush have misunderstood ourselves, if you like, for some time. I'm going to try and put that right."

12:16pm: Where will this leave the Greens' deal with the Gillard Government?

@latikambourke: "Bob Brown - no change to the Greens agreement with Labor to support the Gillard Minority Govt. Says Milne also signatory."

12:14pm: Questions from the floor: Brown says he told the G-G, Julia Gillard, and Tony Abbott of his decision in advance.

12:10pm: New Greens leader Christine Milne is speaking now: "When you reflect on his career, and I've worked with him for a quarter of a century now, he has contributed enormously to the thinking of this country and, in particular, to highlighting the compassion that exists in this country and confronting people with the reality of the need for a more caring, inclusive society."

12:07pm: Bob Brown signing off: "I will be Green until the day I die, if not for a long time after. I am well aware of the size of this decision, but it is, I think, the best wisdom I can muster to have resigned this morning."

"This is a brilliant country. We have a big role to play in both looking after ourselves and making sure our grand-kids have the beautiful heritage that we have now. We have a role to play in a world which seeks peace, democracy and fair go for everyone."

12:05pm: Bob Brown says he's looking forward to heading off for a bushwalk with his partner Paul, to the "snowy tops" of Tasmania's Hartz range. Also on the cards; more photography and writing.

12:03pm: Brown: "I'm 67 and I'm aware that one should always make room for renewal in politics. A democracy is the healthier for the turnover of the depth of talent there is in its community."

12:02pm: Bob Brown says he has been mulling over his decision since the election and decided to step down at the Greens conference in Senegal a fortnight ago.

12:00am: Watch Greens founder Bob Brown announce his retirement.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 6 minutes 33 seconds 6 m Bob Brown announces he is resigning as Greens leader

11:57am: The news broke as Tony Abbott was giving a press conference.

The Opposition Leader said Senator Brown had been a "strong force" in Australian politics.

"I would say too strong a force in Australian politics in recent years ... I think he's had a role in respect of the Greens a little bit like Don Chipp with the Democrats, and I think these will be turbulent times for the Greens if and when he departs."

11:53am: Christine Milne on Twitter: "Bob has been an inspiration to so many. He's been a mentor and a friend to me for 25yrs. I thank him from the bottom of my heart."

"I'm honoured & excited to have been elected leader of the @GreensMPs to build on the great legacy of @SenatorBobBrown, who is retiring today

"A big thank you to my wonderful colleagues @GreensMPs for their unanimous support. I will work hard to honour their trust."

11.48am: Bob Brown, who is 67, made the announcement to his party room colleagues this morning.

Christine Milne will take over the leadership of the party.

"I am sad to leave but happy to go. It is good knowing that the Greens have such a depth of talent and experience lined up for leadership - I could only dream about that a decade ago," Senator Brown said in a statement this morning.

"It is prime time to hand over the reins.

"I offer a huge 'Thank you' to the 1.7 million Australian voters who elected our Green team, and to my nine colleagues."