Embattled federal minister Mal Brough has been forced out of the Turnbull ministry after enduring weeks of pressure over his involvement in the James Ashby/Peter Slipper affair.

Prime Minister Malcolm Turnbull used the cover of the shock resignation of Cities Minister Jamie Briggs, who on Tuesday confessed to acting inappropriately towards a female public servant in a Hong kong bar, to announce Mr Brough had been thrown overboard.

"Mal Brough MP and I have agreed that he will stand aside as Special Minister of State and Minister for Defence Materiel and Science pending the completion of inquiries by the police," Mr Turnbull announced in a statement.

Acting Labor leader Tanya Plibersek immediately proclaimed Tuesday as Mr Turnbull's "taking out the trash day"

"He saved up all the bad news for between Christmas and New Year when he hopes no one is listening," she said.

A cabinet source told Fairfax Media that the government could not risk the Brough scandal dragging into 2016, with no sign of an end to the Australian Federal Police investigation and the Opposition keen to resume its attack when Parliament returns in early February.

"Everyone thought it would be too much of a distraction," the source said.

Finance Mathias Cormann will pick up Mr Brough's portfolio of Special Minister of State and Defence Minister Marise Payne will pick up his second portfolio, Defence Material and Science.

Mr Turnbull is now expected to fill Mr Briggs' vacancy in early 2016, just four months after Mr Turnbull deposed former prime minister Tony Abbott, but it is unclear whether there will be a wider reshuffle and whether Mr Brough's job will be left open for him to return to once the AFP investigation is complete.

A senior Liberal said any reshuffle would hinge mainly on the imminent decision of Deputy Prime Minister Warren Truss. The Nationals leader is due to announce whether he will remain in Parliament for another term or step down, with Barnaby Joyce expected to replace him.

Mr Brough, who remains under investigation by AFP over his role in the copying of the diaries of the former Speaker, Mr Slipper, was a key backer and numbers man in the September leadership coup that saw Tony Abbott replaced as prime minister by Mr Turnbull.

"In offering to stand aside Mr Brough has done the right thing, recognising the importance of the Government maintaining an unwavering focus on jobs, economic growth and national security," Mr Turnbull said.

Labor used the final weeks of Parliament in 2015 to add pressure to Mr Turnbull to dump Mr Brough over the "Ashby-gate" affair.

The Opposition accused Mr Turnbull of "atrocious judgment" in appointing one of his key numbers men Special Minister of State, despite being involved in an ongoing federal police investigation.

The opposition accused Mr Brough, whose ministerial experience goes back to the Howard era, of misleading the Parliament after the minister claimed the Nine Network's 60 Minutes program edited a question put to him, about whether he asked former political staffer James Ashby to make copies of the diary of his then boss Peter Slipper.

Controversy over the diaries flared again in November when Mr Brough was asked to hand over documents relating to the disclosure of Mr Slipper's diary.

Mr Brough, who lost the Queensland seat of Longman in 2007, re-entered Parliament by defeating Mr Slipper in the seat of Fisher in 2013.

Mr Brough did not return calls.