Richard Di Natale has resigned as federal leader of the Greens after almost five years leading the party.

Key points: Richard Di Natale said he was bringing an end to his political career for family reasons

Richard Di Natale said he was bringing an end to his political career for family reasons He has immediately stepped down as leader and will quit the Senate later in the year

He has immediately stepped down as leader and will quit the Senate later in the year He was appointed leader in 2015, taking over from Christine Milne

The Victorian senator will also quit federal politics once his state branch has chosen a replacement for his Upper House seat.

Senator Di Natale cited family reasons for the sudden end to his leadership.

"It's not a decision I have come to lightly, because leading this incredible movement for nearly five years has been one of the biggest honours of my life," he said.

"But my boys are nine and 11 years old now and they've only ever known their dad as a busy and tired, and sometimes grumpy, politician.

"They are growing up quickly and I want to spend more time by their side."

Senator Di Natale was elected to the Greens leadership in 2015 after Tasmanian Christine Milne announced she was quitting federal politics.

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He was elected to the Senate in 2010, having previously contested state election seats in Victoria.

The former GP, who played second-tier Aussie Rules in his 20s, took on the Greens health portfolio and oversaw the party's sport and multiculturalism policies.

"My wife has been a huge support for me in my career and I want to be able to support her in her career," Senator Di Natale said.

Senator Di Natale had time away from the Federal Parliament for a knee operation last year.

He said that time away from politics allowed him to reflect on his future.

Richard Di Natale' said he wanted to better support his partner Lucy Quarterman and sons Ben and Luca. ( ABC News: Sean Davey )

Once it became clear he would not seek preselection for the next election, he decided it was time to leave politics altogether.

"I know this comes as a shock. It has been one of the most difficult decisions of my life, but the time is right," Senator Di Natale said.

"It's right for me and for the boys and for Lucy. The time is right for the Greens, rejuvenation and renewal is very important in politics.

"Our movement is bigger than one person."

Richard Di Natale says he wants to spend more time with his family away from federal politics. ( ABC News: Sean Davey )

Senator Larissa Waters, from Queensland, and Victorian MP Adam Bandt were the party's co-deputy leaders under Senator Di Natale.

Mr Bandt confirmed his candidacy a short time after Senator Di Natale announced his resignation.

Senator Waters said she would nominate to remain as the party's deputy leader.

Larissa Waters is among the frontrunners in contention to replace Richard Di Natale. ( ABC News: Nick Haggarty )

Senator Di Natale declined to say who he wanted to replace him as leader.

The Greens will determine the party's next leader on Tuesday.

Senator Di Natale expects the Victorian Greens will have elected a replacement for his seat by the middle of the year.