Malcolm Turnbull says he's sorry a female assistant minister was dumped from her own seat, but he won't intervene to save her.
Jane Prentice on Saturday lost to her former staff member, Brisbane City councillor Julian Simmonds, as the Liberal National Party's candidate for the Brisbane seat of Ryan.
As the latest polls showed Mr Turnbull has jumped well ahead of Bill Shorten as preferred prime minister, he said it was up to local Liberal Party members to choose their representatives.
"We're very sorry to see Jane's been defeated in the preselection, but this is the consequence of having a grassroots political party," Mr Turnbull told reporters on Monday.
Queensland MP Warren Entsch said Ms Prentice's dumping was "a bloody disgrace" and he was profoundly disappointed by it.
"She doesn't deserve it and I think it sends a very, very bad message with regards to women in politics in Queensland," he said.
Fellow Queenslander, Michelle Landry, said she was "totally appalled" at Ms Prentice's dumping.
"We've hardly got any federal females in Queensland in the government and one has been pushed aside by a young male," she told the ABC.
Home Affairs Minister Peter Dutton, who provided a written reference supporting Ms Prentice, said the party was a democracy.
"There were over 350 people at the preselection, many of them women," he told reporters.
"They looked at the merits of the individual candidates and they made a decision."
The Newspoll released on Monday gave Mr Turnbull his best preferred prime minister result since the 2016 election.
His approval was up eight percentage points to 46 per cent, against Labor opposition leader Bill Shorten on 32 per cent.
But despite splashing out on personal tax cuts, the coalition still trails Labor 49-51 per cent on a two-party preferred basis, the poll published in The Australian shows.
A separate Ipsos poll published by Fairfax Media puts the coalition in an even worse position against Labor at 46-54 per cent, which is a decline from 48 per cent in April.
But Mr Turnbull did increase his Ipsos lead as the preferred prime minister to 52 per cent, against 32 per cent for Mr Shorten.
And asked if they thought they would be better off under the new budget, 38 per cent of the 1200 voters polled by Ipsos believed they would.
The polls follow Labor and coalition income tax cut promises during budget week and a citizenship crisis that forced four Labor MPs to resign from parliament.