Federal Trade Minister Andrew Robb will retire from politics at this year's election, and Nationals Leader Warren Truss will reveal his future plans today, as Prime Minister Malcolm Turnbull prepares to reshuffle his frontbench.

Key points: Trade Minister Andrew Robb to retire from politics at federal election

Trade Minister Andrew Robb to retire from politics at federal election Robb could stand down from ministry tomorrow

Robb could stand down from ministry tomorrow Warren Truss also expected to announce retirement tomorrow

Warren Truss also expected to announce retirement tomorrow Barnaby Joyce likely to assume Nationals leadership

"I'm 64 and in excellent health, I feel I've got another career left in me" Mr Robb told 7.30 last night.

"There's things I want to do, particularly in the private sector and some in the mental health space, and I didn't want to leave that too late.

"After 12 fulfilling and eventful years I feel the time is right."

Mr Robb, who said he made his decision at Christmas last year, said he had been approached by Mr Turnbull to remain in the trade portfolio for the time being.

"He has said to me that he would like me to stay on for some time, some months, perhaps, so that I can try and complete a couple of important areas of business that I have got to a fairly advanced stage," he said.

Mr Robb has sealed trade deals with China, Japan and South Korea, and signed the Trans-Pacific Partnership (TPP) agreement in New Zealand last week.

"I will leave politics in the comfort of knowing that both the Turnbull Government and the Coalition are in great shape," he said.

"I have been given some wonderful opportunities to serve our country by both Tony Abbott and Malcolm Turnbull, and for that I will be eternally grateful."

Mr Robb, who took a three-month break in 2009 to seek treatment for depression, said the area of mental health needed more attention in the community.

"Mental health is, I think ... probably the area that's had the least focus on it in the whole area of health for decades," he said.

Mr Robb said while the stigma of mental health was being broken down, there was still a long way to go.

"It's not satisfactorily dealt with yet, but we have made a lot of progress," he said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 7 minutes 16 seconds 7 m Andrew Robb to focus on mental health after retiring from politics

In a statement, Mr Turnbull said he had been "the most successful trade minister in the country's history".

"These agreements are driving and securing strong economic growth into the future," he said.

"Andrew is engaged in ongoing free trade negotiations with important trade partners, which we hope to bring to a successful conclusion in the not too distant future."

Mr Robb was viewed as a strong performer in both the Abbott and Turnbull ministries.

He was head of the National Farmers' Federation and a previous federal director of the Liberal Party before being elected to the Victorian seat of Goldstein in 2004.

Environment Minister Greg Hunt praised Mr Robb's achievements.

"I don't think anyone has done as good a job as trade minister for Australia," Mr Hunt told Melbourne radio station 3AW.

"My view is Andrew has earned the right to stay as long as he wants. All praise to Andrew, I mean what a career."

Truss also expected to retire at next election

Mr Truss is also widely expected to retire from Parliament at the next election and will announce his future plans today.

There has been speculation for months Mr Truss would step aside as leader.

There has been speculation for months Mr Truss would step aside as leader before the next Federal election. ( ABC News: Nicholas Haggarty )

His move is expected to trigger a series of changes within the Nationals, with Barnaby Joyce tipped to replace him as leader.

The regional party is also pushing for another seat in Cabinet, arguing their numbers in the Coalition partyroom entitle them to four positions.

Mr Truss was elected as member for the Queensland seat of Wide Bay in 1990 and has led his party since 2007.

Indigenous Affairs Minister Nigel Scullion, who is also a member of the Nationals, said he would be sad to see Mr Truss move on.

"If it's the case that Warren Truss will make a decision shortly, that he'll leave, it'll be a great loss. He's made a wonderful contribution to public life," he said.

But he said movement was good for government.

"From time to time you do get movement and it's like a footy team, a strong footy team. You've got young people coming up, but eventually you've got to go and make that move," he said.

"We're very lucky in the Coalition that we have such a depth of talent.

"I think if anything it'll have a positive effect on government."

Opposition Leader Bill Shorten said the changes were indicative of a "Cabinet in chaos".

"It's only a matter of time before Malcolm Turnbull stands in his courtyard to tell Australians that 'good government starts today'," he said.

"Malcolm Turnbull should be focused on Australian jobs, but he is completely paralysed by ministers who are only worried about their own."

The shake-up follows former cities minister Jamie Briggs' resignation from the frontbench last year after an incident with a public servant in Hong Kong, and Mal Brough standing aside as special minister of state while federal police investigate the Peter Slipper affair.

The future of Human Services Minister Stuart Robert is also uncertain, with a review underway into a controversial trip to China in 2014.

Mr Robert maintains it was a private visit, despite meeting with senior Chinese officials, as well as witnessing a mining deal with a major Liberal Party donor.