Nationals MP Fiona Nash, her party's new deputy leader and first woman to hold the job, Victorian Nationals MP Darren Chester and Queensland Liberal Steve Ciobo are the biggest winners of the shake up, moving into the cabinet.

Ms Nash will be minister for Rural Health, Regional Communications and importantly, Regional Development. Mr Chester becomes Minister for Infrastructure and Transport and Mr Ciobo becomes Trade Minister, on the recommendation of Mr Robb - who becomes special envoy for trade between now and the election.

Announcing the reshuffle, Mr Turnbull said his new team was "dynamic" and combined youth, new talent, experience, and sense of innovation and enterprise.

He also noted that there are now "six women in the cabinet, 10 in the executive, and both deputy leaders of the Liberal and National Party for the first time in Coalition history".

"This is a revitalised government and it is revitalised because of new blood, new talent coming in."

The reshuffle comes after difficult fortnight in parliament which saw the Turnbull government under pressure over tax reform and ministerial standards, and the resignation of senior minister Andrew Robb and Nationals leader and deputy prime minister Warren Truss.

The Turnbull government has lost five ministers in total - Mr Truss, Mr Robb, former cities minister Jamie Briggs who resigned in December, former human services minister Stuart Robert who resigned days ago and former special minister of state Mal Brough, who resigned earlier on Saturday.

Mr Brough, who was Special Minister of State and 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.

He 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.

"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.

Mr Turnbull has rewarded both supporters who backed him to become leader in September last year, as well as people who backed former prime minister Tony Abbott.