Andrew Robb, Australia's minister for trade and investment, speaks during a Reuters interview at a hotel in Manila May 21, 2015. Reuters/Romeo Ranoco

Minister for Trade and Investment Andrew Robb announced on Wednesday that he would retire from federal politics following the next election, saying he believes “the time is right.”

The 64-year-old says he is in “excellent health” and plans to move on to a career in the private sector after “12 fulfilling and eventful years” in government.

Speaking to the ABC’s Leigh Sales on Wednesday night, Robb said he leaves politics “in the comfort of knowing that both the Turnbull Government and the Coalition are in great shape.”

The retiring Minister added that it was an opportune time to give way to the “talented next generation” of the Liberal party.

“There’s a great team coming through and it’s their turn I think,” he said.“We’ve got some real talent in the ministry and the backbench, and it’s time I think to hand over the baton.”

Robb also told Sales of his plans to advocate for, and contribute to, the mental health sector, and that leaving these endeavors until the next term at age 68 would be “too late.”

“Mental health is I think the one area that has the least amount of focus on it in the whole area of health for decades,” he said.

“The stigma has been broken down and that is leading to more people being prepared to step up, more champions for the sector and more money coming in.”

In a feature article by the ABC, Robb spoke in detail of his 40-year battle with depression and its impact on his career in politics and the public eye.

"I wanted to show people that you can deal with depressive conditions and even come back to the same job, or even a job with greater responsibility,” he said.

"I've now had nearly five years where I've had better days than almost any time in the last 45 years. I've got more responsibility I suspect than any time in my life and I think I'm reasonably effective in what I've been doing.”

Robb told Sales on Wednesday that he believes “there is still a long way to go” in breaking down the stigma of mental illness, particularly for those in positions of authority.

He also said Prime Minister Malcolm Turnbull has asked him to stay on “for some months”, and there is no word yet on who will replace Robb as Trade Minister, although there are talks of Environment Minister Greg Hunt and International Development Minister Steve Ciobo running for the position.

Human Rights Commissioner Tim Wilson and lawyer Georgina Downer - daughter of former foreign minister Alexander Downer - are also tipped to be jockeying for Goldstein, Robb’s blue-ribbon Melbourne seat.

Robb’s retirement announcement was quickly followed by another, as Nationals Leader Warren Truss also revealed his plans to leave politics.

A reshuffling of PM Turnbull’s cabinet is now expected over the weekend, as Robb and Truss’ departures leave the Liberal party facing a period of political instability.

According to The Australian, a vote on Truss’ replacement as party leader is projected to take place tonight at a Nationals meeting at 8pm AEDT.