UPDATE: Senator Richard Di Natale has been elected as the new leader of the Greens.
Queensland Senator Larissa Waters and Scott Ludlam have been elected co deputy leaders of the party.
Earlier, Greens leader Christine Milne has resigned as leader of the minor party after three years in the job.
Sen Milne told the party room this morning of her decision, saying she had achieved what she wanted to achieve in the role.
The Tasmanian has been leader since Bob Brown retired from the role in April 2012, and her decision will bring to an end her 25 years in politics across both the Tasmanian Parliament and federal Senate.
She said her decision was made with "a mix of optimism, pride, excitement and sadness", and she planned to spend more time with her family and grand-children.
But Sen Milne said she was not hanging up her political boots altogether.
"Life after parliament is not however, life after politics. The fight for action on global warming will continue and I will take my passion, and all that I've learnt, to that fight standing shoulder to shoulder with the community here, and all over the world, for climate justice," she said.
A ballot for The Greens leadership will be held later this morning, with a press conference scheduled this afternoon.
Treasurer Joe Hockey said he did not know of the reasons behind Senator Milne's decision.
A leadership ballot is expected to be held at 11.30am AEST.
Adam Bandt is expected to be the frontrunner for the position.
CHRISTINE MILNE'S STATEMENT IN FULL
It is with a mix of optimism, pride, excitement and sadness that I am resigning the leadership of the Australian Greens and leaving the Senate.
I have achieved what I set out to achieve when I took over the leadership. The Greens have gone from strength to strength with solid election results and a growing, engaged party membership.
I promised a more cabinet-style, collaborative approach to leadership. I am so proud of the way my colleagues have responded. We are a strong, capable, visionary Greens team.
We have stood strongly for a safe climate and an end to wealth inequality. We have stood with the community against the cruelty of the Abbott Government, with their first budget resoundingly rejected by the people, and the Senate.
My decision to resign today is one I made with my family. After 25 years in politics, I am looking forward to spending more time in my beautiful home state of Tasmania, with friends and family, and especially as I am soon to be a grandmother.
Life after parliament is not however, life after politics. The fight for action on global warming will continue and I will take my passion, and all that I've learnt, to that fight standing shoulder to shoulder with the community here, and all over the world, for climate justice.
I would like to say thank you. To my family, staff, colleagues, friends, party members, supporters and voters - thank you. I have cherished your input, your passion, and your support.
Update your news preferences and get the latest news delivered to your inbox.