Deputy Prime Minister Warren Truss has confirmed his retirement from federal parliament, creating a vacancy for the leadership of the Nationals.
It comes as Cabinet minister Andrew Robb also announces plans to leave government at the next election.
Mr Truss told parliament he would leave at a time convenient to the government, likely within the next few days.
It had been a great pleasure and privilege to be a member of federal parliament, he said on Thursday as Prime Minister Malcolm Turnbull and other MPs looked on.
Mr Truss thanked the voters of his Wide Bay electorate in Queensland for having elected him nine times.
"I was always talked about as the youngest national president of rural youth, the youngest counsellor, youngest mayor, but now that I'm numbered amongst the oldest, I think it's time to go," he said.
"When I became leader in 2007, nobody wanted the job, including me."
Despite taking the leadership reluctantly, Mr Truss said it had been an honour to head the Nationals.
After losing the 2007 election, the party's numbers had declined and the media was predicting the party was "finished", he said.
"When I became leader in 2007, nobody wanted the job, including me," he said.
"I am pleased to say that now things are different, and everyone wants the job."
Mr Truss said he had special memories from each portfolio during his more than 12 as ministers, most of them in cabinet.
He started as a junior minister in the industry portfolio, and was the first minister with special responsibility for Centrelink.
"The idea that a government department should be there to look after people might seem pretty elementary in this day and age but it was a major challenge at the time."
Mr Truss reflected on his time as agriculture minister, a portfolio he admits he never wanted.
"I knew how farmers treated their agriculture ministers, particularly when they were Nationals," he said.
"You just simply cannot achieve what your constituency expects of you."
However, the time had been eventful, with foot-and-mouth disease outbreaks in the United Kingdom and severe drought, he said.
He established the "most generous" drought assistance package that had ever been provided, which he believes helped a lot of farmers through a situation they otherwise couldn't have managed.
Mr Truss said his time as trade minister was his least fulfilling, admitting his achievements were small in comparison to Liberal minister Andrew Robb.
Mr Truss received a standing ovation from all MPs in the chamber, and warm handshakes from Labor leader Bill Shorten and opposition frontbencher Anthony Albanese.
Prime Minister Malcolm Turnbull heaped praise on Mr Truss, citing his commitment to the coalition and his advocacy for his local electorate.
"He understands the importance of the National Party's distinct identity, but the reality that we are so much stronger when we are working closely together," he told parliament.
The prime minister recited lines from his deputy's maiden speech to parliament in 1990, saying Australia had become a much luckier country.
Mr Shorten commended Mr Truss for his handling of the still-missing Malaysia Airlines flight MH370.
"You're warm, you're dry, you are often self-deprecating," he told parliament.
"You've got a great sense of humour and you have an ability to craft a meaningful, empathetic response."
Agriculture Minister Barnaby Joyce is widely tipped to take over the Nationals leadership, which comes with the deputy prime minister role while the coalition is in government.
But the race is open for the Nationals deputy leadership.
Robb leaving politics with no regrets
Cabinet minister Andrew Robb has also announced he will leave federal politics at the next election, but stay on as trade minister for the time being at the request of Prime Minister Malcolm Turnbull.
"I'll leave with no regrets," he told reporters in Canberra on Thursday.
"I'm not a spring chicken, so I want to move one."
Mr Robb said he would have felt a greater obligation to stay had the government not been in such great shape.
"I think the talent coming through is outstanding."
The regeneration of the government after a bruising Liberal leadership challenge in September had created a better esprit de corps.
Some of the younger MPs promoted to the ministry had hit the ground running and were making a very strong contribution.
"And we've got more putting pressure on them coming up through," Mr Robb said.
