Australian Greens party leader announces shock resignation, PM Abbott pays tribute to her

Australian Prime Minister Tony Abbott has paid tribute to departing leader of the Greens party Christine Milne who announced her shock resignation on Wednesday.

Senator Milne, who had led Australia's third-largest political party for three years, broke the news on social media with a tweet saying "Feeling optimistic, proud & sad to announce I'm not contesting 2016 election, and so I resign as Leader of Australian Greens."

In a vote taken by the 11 federal Greens MPs, doctor and public health expert Richard Di Natale was elected as leader while Queensland senator Larissa Waters and West Australian senator Scott Ludlam were elected as "co-deputy leaders".

Deputy leader Adam Bandt, the party's only lower house MP to be re-elected in the party's 23-year history, did not contest the deputy position.

Prime Minister Tony Abbott praised Milne who began her career in state politics 25 years ago.

"We come from very different political traditions but I respect Christine Milne as I respect all senior members of the Parliament, " he said.

"It takes a great deal of commitment and patriotism to offer to serve in the Parliament."

In a statement, Milne said she had achieved what she had set out to achieve since taking over the leadership from the party's inaugural leader Bob Brown in 2012.

"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," Milne said on Wednesday.

Milne, 61, is the only woman to lead a party at both the federal and state levels. Endi