Former NSW Parliamentary Secretary for the Hunter Catherine Cusack attacked Scott Morrison's handling of the recent flood emergency, accusing him of politicising the tragedy.

"I can't vote for Scott Morrison, full stop, at the next federal election," she told the ABC.

"Doing the right thing now won't get my vote because it won't undo the wrong he has done to my community."

Ms Cusack said Mr Morrison had forced the Liberal federal executive to take over the party's state division to ensure his candidates were preselected in NSW and therefore robbed every person in those seats "their rights to have a voice in the candidate selection".

"That behaviour, in terms of his own party and his own colleagues, is completely unacceptable," she said.

"He is now using his role as prime minister to bully the NSW government and the flood victims because he is not getting his way."

Ms Cusack said this was evident in the political appointment of Shane Stone as the coordinator-general of the National Recovery and Resilience Agency and using guidelines to exclude some flood victims.

The state upper house member also accused Mr Morrison of failing to engage with the NSW government to assess and approve payments and co-fund a recent disaster package, saying last month she would quit the party in protest.

"As a result, those packages are well below what's required and what should be available," she said.

"It is unbelievable anyone would act like this towards flood victims."

Deputy Prime Minister Barnaby Joyce told the Newcastle Herald during a visit to the Hunter on Tuesday that "Catherine Cusack was never really happy in the Liberal party for a long while".

Mr Joyce is one of several MPs, including former NSW Liberal premier Gladys Berejiklian, Liberal senator Concetta Fierravanti-Wells, One Nation leader Pauline Hanson and independent senator Jacqui Lambie, to have questioned Mr Morrison's character.

The Nationals leader said in text messages leaked this year that Mr Morrison was a "hypocrite and a liar".

"I have never trusted him, and I dislike how earnestly [he] rearranges the truth to a lie," the message from March last year said.

Asked about Ms Cusack's vow to vote for someone other than Mr Morrison, Mr Joyce said: "That's her choice. Obviously she must be voting for Mr Albanese."

Ms Berejiklian sacked Ms Cusack as Parliamentary Secretary for the Hunter last year after she voted against a controversial land management bill.

Ms Cusack has been a member of the NSW upper house since 2003.

Her comments came as new polling showed last week's budget had failed to improve the government's popularity with voters.

A Roy Morgan Poll conducted in the past week shows Labor extending its lead to 57-43 in two-party preferred terms, a 1.5 percentage point increase from a week earlier.

Senior Labor figures tried to play down their lead in the polls.

Frontbencher Chris Bowen said the party needed to "win seats, not polls".

Mr Bowen also took aim at the Prime Minister's trustworthiness as the Liberal Party infighting continued.

"Sure, there's a pile-on, but it's coming from his own side," he told the ABC.

Assistant minister Tim Wilson defended Mr Morrison, saying he was confident of holding government.

"It's just not even remotely relatable to any experience," he told the ABC.

"I've always found my engagements with him to be incredibly professional and engaged in good faith."

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