South Australian federal MP and cities minister Jamie Briggs has quit the frontbench due to allegations made by a public servant while on an official trip overseas.
The incident relates to an "error of professional judgement" that occurred in a Hong Kong bar late at night with a female public servant.
Mr Briggs' resignation comes simultaneous to news that Mal Brough will step aside from his portfolios pending a police investigation into actions surrounding former speaker Peter Slipper and staffer James Ashby.
The member for the seat of Mayo said at press conference today he would resign because his behavior "Did not meet the high standards of ministers in his government."
"At no point was it my intention to act inappropriately … nothing illegal was alleged," Mr Briggs said, adding the woman "raised concerns about his behaviour".
"This was an error of professional judgement," he said but did not provide specific detail about his actions.
The public servant was not named, but Mr Briggs said the decision to resign came after meeting with Mr Turnbull.
Mr Briggs said his behaviour was unbecoming of someone who held high office.
A statement from Mr Turnbull said: "Ministers are expected to uphold high standards of behaviour as set out in the Ministerial Standards."
"On this occasion his conduct fell short of that standard.
"After being invited to reflect on his position, he offered his resignation which I have accepted.
"While disappointed by the conduct that led to his resignation, I thank Mr Briggs for his capable service as a Minister.
"I look forward to Mr Briggs continuing to make a valuable contribution to the work of the Government in the future,"the PM's statement said.
Environment Minister Greg Hunt will act in the Cities portfolio.
Mr Briggs, 38, was almost dumped from the ministry during the reshuffle that took place when PM Abbott was rolled in September, but Mr Turnbull gave him the Cities and Built Environment portfolio.
He previously held the role of Assistant Minister for Infrastructure and Regional Development.
Mr Briggs has held the seat in the Adelaide Hills since a 2008 by-election following the former foreign minister Alexander Downer's resignation.
Mr Brough has also stepped aside from his roles as Special Minister of State and Minister for Defence Materiel and Science pending a police investigation.
There had been calls for Mr Brough to resign after he provided contradictory statements of justification for his involvement in the procurement of the extracts from then-speaker Slipper’s official diary.
Senator Mathias Cormann will take over his role as special minister of state and defence minister, Senator Marise Payne, will act as Minister for Defence Materiel and Science, Mr Turnbull's office said in a statement.