Canberra, May 6 (IANS): Australian Prime Minister Tony Abbott has paid tributes to Greens party leader Christine Milne who announced her shock resignation on Wednesday.

Senator Milne, 61, 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 leader while Queensland senator Larissa Waters and West Australian senator Scott Ludlam were elected as "co-deputy leaders", Xinhua reported.

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 for 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.

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