* Popular lawmaker to leave at next election due by May
* Bishop says government will win re-election
* Follows four government MPs who have retired or defected
* Ruling coalition is in a minority and trailing in polls
(Adds details, reaction quotes; paragraphs 2,6-9,11,12)
By Colin Packham
SYDNEY, Feb 21 (Reuters) - Australia's former foreign minister, Julie Bishop, will retire at the next election, she said on Thursday, joining a wave of lawmakers leaving a government that faces defeat in the poll, due by May.
The departure of one Australia's most popular and high-profile female lawmakers follows four government MPs either retiring or defecting from the ruling centre-right coalition, which is in a minority and trailing in polls. other female members of the Liberal Party have also left amid claims of disunity, bullying and intimidation, although Bishop praised the government in her retirement speech.
"It is my view that the Liberal-National coalition will win the next election because it is focusing on the things that matter to the Australian people," Bishop told parliament, listing policy achievements from the economy to security.
"And on that basis, I have reconsidered my position... I will not re-contest the seat of Curtin at the next election."
Bishop has represented Curtin, a constituency in Western Australia, since 1998. She was foreign minister from September 2013 to August 2018, and deputy leader of the Liberal Party, which governs in coalition with the Nationals.
The timing of Bishop's departure heaps pressure on a government that is lagging in opinion polls, although the gap has lately narrowed, and which is battling a perception it is out of touch, especially with female voters.
"Bishop will take a large number of votes with her," said Haydon Manning, a professor of politics at Flinders University in South Australia.
"There will be people who would have voted for Bishop, no matter what. Those will now be open to the opposition Labor Party."
In January, Minister for Women Kelly O'Dwyer said she would retire, after backbencher Julia Banks quit the party late last year to sit as an independent, protesting against its treatment of women and policies on energy and climate change. who resigned both her posts after a backbench revolt last August forced then prime minister Malcolm Turnbull from power, was defeated in a party vote to replace him, with then treasurer Scott Morrison succeeding instead. and Turnbull both praised Bishop.
"You have been our finest foreign minister - eloquent, elegant and always courageous advancing our national interest in these challenging times," Turnbull said in a message on social network Twitter.