Prime Minister Malcolm Turnbull is expected to announce a revamped frontbench on Saturday that will promote a swag of younger MPs and increase the number of women in the cabinet.
Special Minister of State Mal Brough, who is also minister for Defence Materiel and who stood aside from the ministry last December because of his involvement in the James Ashby/Peter Slipper affair, resigned on Saturday ahead of Mr Turnbull's reshuffle.
Fairfax Media has been told that Queensland MP Steve Ciobo is all but certain to move from his international development junior ministry and enter cabinet, picking up the trade portfolio vacated by Andrew Robb.
Victorian Nationals MP Darren Chester, now the Assistant Defence Minister, is expected to pick up the portfolios of infrastructure and transport vacated by outgoing party leader Warren Truss.
New Nationals deputy leader Fiona Nash – the first woman to be part of the country party's leadership group and who now holds the Rural Health post in the outer ministry – will also enter an expanded cabinet, which grows from 21 to 22 people.
Ms Nash will become Minister for Regional Development, overseeing the stronger regions fund that has at least $200 million in it, as well as the Minister for Rural Communications and she will keep the Rural Health portfolio.
Mr Ciobo is 23 years younger than Mr Robb, the man he will replace, and Mr Chester is 18 years younger than Mr Truss, the man he will replace.
Announcing his resignation, Mr Brough said he was disappointed to stand down but did not expect the AFP investigation into the matter would finish for several more months and that it was not appropriate for the two portfolios to be left open. He again denied any wrong doing.
Today I announced my resignation as Minister in the Turnbull Government https://t.co/ceUW6wpUkj #auspol— Mal Brough (@MalBrough_MP) February 13, 2016
" Portfolios should not be left open, it was generous of the Prime Minister to allow me to step aside when I asked but now is the right time given that the police have informed me that it is going to take so much longer than anyone could have anticipated," he said.
Other MPs expected to be promoted include the Assistant Minister to the Prime Minister, Alan Tudge, who is expected to move to a more senior position in the outer ministry, as is Assistant Science Minister Karen Andrews.
Assistant Ministers Concetta Fierravanti-Wells, Scott Ryan and James McGrath are tipped for promotion.
Backbench Liberal MPs Dan Tehan and Angus Taylor are also tipped for promotion to the assistant ministry level, and so are National backbenchers Matthew Canavan and Keith Pitt.
Senator Canavan is expected to be appointed the assistant minister for Northern Australia, and Mr Pitt assistant minister to party leader Barnaby Joyce.
The reshuffle has been caused by the retirement of Mr Robb and Mr Truss, and by the need for Mr Turnbull to replace former cities minister Jamie Briggs who stepped aside last year after an incident in a bar in Hong Kong and by the resignation of human services minister Stuart Robert this week over a breach of ministerial rules during a trip to China.
Vocational Education Minister Luke Hartsuyker, a Nationals MP who is also deputy leader of the house and was a candidate for the party's deputy leadership last week, has been dumped from the frontbench.
The reshuffle offers Mr Turnbull a chance to refresh his frontbench team ahead of the federal election later this year..
Opposition leader Bill Shorten said the cabinet was in "chaos" and asked, since Mr Turnbull was elected "what's happened? What has he actually done?"
"We know that he's 13 or 14 ministers down over the last 6 months. We know their are brand new people into major cabinet portfolios and expecting them to get up to speed by the time of the budget. That is diabolical for the budget preparation and what we see is a divided government," he said.