New South Wales Greens senator Lee Rhiannon has announced she will retire in mid-August to make way for current state Upper House MLC Mehreen Faruqi.

Key points: Lee Rhiannon lost number one preselection spot on the NSW Senate ticket in November last year

Lee Rhiannon lost number one preselection spot on the NSW Senate ticket in November last year That came after a dispute with Greens colleagues about Gonski 2.0 negotiations

That came after a dispute with Greens colleagues about Gonski 2.0 negotiations Senator Rhiannon says her replacement, Mehreen Faruqi, will bring a wealth of experience to the Senate

Senator Rhiannon has been a divisive figure for the party in the past 12 months.

In November last year she lost the number one preselection spot on the party's NSW Senate ticket to Ms Faruqi, after she was excluded from the party room over a bitter split with colleagues who accused her of undermining the Greens' Gonski 2.0 negotiations.

The dispute centred on Senator Rhiannon's May decision to campaign and vote against the Gonski 2.0 funding package.

At the time, the Greens were negotiating with the Turnbull Government over the $23.5 billion schools funding package.

The party eventually decided to vote against it.

But Senator Rhiannon has wished her successor well, and said she looks forward to continuing to work together.

NSW Greens MP Mehreen Faruqi took the top spot on the NSW Senate ticket last year. ( Supplied )

"I always put the party first and the best chance we have is for Mehreen to be a sitting senator coming into the next election," Senator Rhiannon said.

"It's critical that we continue to be represented in New South Wales by the Greens."

Greens leader Richard Di Natale thanked Senator Rhiannon and said she had devoted her life to fighting for a better world.

He praised Senator Rhiannon's work on political donations reform and animal welfare.

Senator Rhiannon said she was not looking to move back into NSW politics and did not have any other roles planned at this stage.

"In resigning from Parliament I'm not resigning from politics, I'm passionate about many of the issues that I have worked on," she said.

"I don't have anything immediately planned, but you don't have to have a position to be able to work on issues around free public education, climate action, and union rights. I will continue to turn up, participate and assist where I can."

Senator Rhiannon — currently the oldest woman serving in Federal Parliament — said she had always believed, "a core part of the work of the Greens is building and supporting progressive campaigns".

"When I was young, parliament was where we went to protest, not to get a job," she said.

"My years as an MP have strengthened my belief that it is people's action that drives progressive social change."

Liberal senator Jane Hume tweeted a message of support for Senator Rhiannon, saying she had had, "a tough road in the Greens" but had always been, "courteous and considered".

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Labor's Andrew Giles also tweeted, saying he had been "fortunate to work alongside" Senator Rhiannon.

"I'll miss her, after August, and wish her all the best," he said.