Prime Minister Malcolm Turnbull has led the tributes for retiring cabinet ministers Warren Truss and Andrew Robb, describing them as "remarkable men" who have helped shape Australia.
In a speech in Parliament on Thursday, Deputy Prime Minister and Nationals leader Warren Truss confirmed he will move to the backbench in the coming days and will not contest the next federal election.
Officially ending months of speculation about his future, Mr Truss' decision paves the way for Agriculture Minister Barnaby Joyce to take the Nationals' leadership. The party will meet at 8pm tonight to choose the replacement.
Mr Truss said it was an honour to serve as Nationals leader - although he revealed he was initially reluctant to take the job.
"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."
First elected in 1990, Mr Truss took over the Nationals leadership from Mark Vaile in 2007, when the Nationals were at a low ebb. His task was to overcome the perception the party was in terminal decline and rebuild.
Mr Truss became Deputy Prime Minister when the Coalition won power in 2013.
"I wonder whether I'll be the last person with a limited education who comes from one of the poorest electorates in the country to become Deputy Prime Minister. I hope not, because I think we do need amongst the leadership of our country, a breadth of experience and skills," he said.
Mr Robb announced his plans to leave Parliament on Wednesday. He is expected to stay in cabinet until the next election.
Mr Turnbull said both men played an enormous part in creating the nation we are today and their departure was a "watershed" moment.
"They have made Australia different. They've made Australia better. They've shaped Australia. They've shaped our future, whether it is in trade or it is in infrastructure or in their example of clear, warm, humane patriotism, a love of country," he said.
Mr Turnbull praised Mr Truss' commitment to the Coalition.
"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 described Mr Robb as "the most successful Trade Minister in our history".
Opposition Leader Bill Shorten praised Mr Truss for the "dignified" way he handled the MH370 plane disappearance.
He also lightened the mood by talking about the time Mr Truss was name-checked on the hit TV series Lost.
In the first episode of the show, a detective with a dodgy Australian accent tells a character that the man he just headbutted in a bar was Mr Truss.
"For some reason I'm just not sold on the image of Warren Truss, bar-room brawler. The man that we know and pay tribute today is a kinder, gentler soul," Mr Shorten said.
Mr Joyce said Mr Truss was a "decent man, a gentle man, a good man".
