Supporters of former prime minister Tony Abbott are agitating for him to be promoted as part of a wider ministerial reshuffle in 2016.

Key points: Timing of reshuffle depends on an expected announcement by Warren Truss that he will retire

Timing of reshuffle depends on an expected announcement by Warren Truss that he will retire Coalition sources are divided on whether Jamie Briggs will return to the frontbench

Coalition sources are divided on whether Jamie Briggs will return to the frontbench Speculation Dan Tehan, Scott Buccholz and Alan Tudge could be in line for promotions

Speculation Dan Tehan, Scott Buccholz and Alan Tudge could be in line for promotions Voters call for truth behind Briggs' resignation

A new-look frontbench is expected to be unveiled in the first few months of the new year, triggered by the sudden departure of Jamie Briggs and Mal Brough.

Former employment minister Eric Abetz, a political ally of Mr Abbott, said the former prime minister should be considered as part of a government reshuffle.

He told NewsRadio he would welcome Mr Abbott's return to Cabinet.

"I'm on the record as saying that I believe Tony Abbott has more to offer public life in Australia," he said.

"I hope that he stays in the Parliament and I hope that there will be a place for him, a prominent place for him, in any future ministry should he decide to stay."

That call has been echoed by Nationals Senator John Williams, who told RN Breakfast he would welcome Mr Abbott's return to the frontbench.

"If Tony Abbott went back into cabinet it would be a good way to heal the wounds of the past," he said.

The prospect of Mr Abbott returning to the frontbench was downplayed by Health Minister Sussan Ley.

"People can make a contribution from wherever they sit in the Parliament, and I think that's an important point, but matters for ministerial appointments is entirely for the Prime Minster," she said.

"I know that Tony Abbott will continue to make an extremely important contribution, whatever he does in Parliament in the future."

Two investigations conducted into Briggs' conduct

Mr Briggs resigned as Minister for Cities and the Built Environment after a complaint was made about his behaviour towards a female public servant at a bar in Hong Kong.

The incident occurred during an official visit in November.

The ABC understands the Prime Minister's office became aware of the allegations surrounding Mr Briggs several weeks ago.

Two independent investigations have since been conducted into the issue, after a formal complaint was lodged.

The official has not been publicly identified and the precise nature of her complaint has not been revealed.

In a separate development, Mr Brough, the Special Minister of State, also stood aside because of a police investigation into the copying of former speaker Peter Slipper's diary.

It is understood the process involving Mr Brough was already in train when the accusations against Mr Briggs first came to light.

Acting Opposition Leader Tanya Plibersek questioned the time it took for Mr Brough to stand aside from the frontbench.

She said Mr Turnbull had mishandled the situation.

"It's completely unacceptable. It shows a Prime Minister who's not prepared to face up to his responsibilities, who's not prepared to be straight with the Australian people about why he's made this decision, and it shows a shocking lack of judgment in the first place, in appointing Mal Brough," she said.

Sorry, this video has expired Turnbull showed 'poor judgement' over Brough, Briggs affairs: Plibersek

Briggs' political future divides coalition

Supporters of Mr Briggs predict he will eventually make a return to the frontbench.

The LNP's Ewen Jones described him as a man of "huge talent".

"The cream will rise and Jamie will come back," Mr Jones said.

"He has got time on his side ... when you have someone of good talent like Jamie Briggs, it's a shame to miss him."

Mr Jones said while Mr Briggs has paid the penalty, he has friends in Parliament "that will stand by him".

However Nationals Senator John Williams disagreed, claiming Mr Brigg's departure would not be a great loss to the frontbench.

"With Briggs leaving it means there will be no deterioration in the overall quality of the ministry, in fact it should improve," Senator Williams said.

Reshuffle hinges on Truss making announcement on his future

The timing of the wider ministerial reshuffle depends on Deputy Prime Minister Warren Truss.

The ABC has been told the shake-up will wait until Mr Truss makes an announcement about his political future, which will be made within the first quarter of next year.

It is predicted he will retire from politics at or before the next federal election, with Agriculture Minister Barnaby Joyce tipped to take over as leader of the Nationals.

The Nationals have continued to lobby for another spot in the ministry, despite a failed attempt by the LNP's Ian Macfarlane to change party rooms within the Coalition.

The reshuffle would also be an opportunity to promote new talent to the front bench, although no final decision has been made on any possible candidates.

Some Government MPs have predicted the likes of Dan Tehan, Scott Buccholz and Alan Tudge will be in line for promotions.

Brough 'disappointed' by AFP investigation

In a letter to the Prime Minister, Mr Brough said he took the decision to stand aside because he had not been given a timeline about when the AFP's investigation would finish.

"It disappoints me that this matter hasn't been resolved by this time as all facts have been in the public domain for years and the public statements of Mr Ashby confirm my position that at no time did I counsel or procure him for any improper purpose," he said in the letter.

"I look forward to resuming my ministerial responsibilities and assisting with the important work of Government once the investigation is complete."

Mr Brough said the AFP has told him the earliest they could interview him about the allegations was after January 5, 2016.