Former deputy prime minister and Nationals leader Mark Vaile became yesterday the latest Howard government high-flyer to quit federal politics.

Mr Vaile said the drivers behind his decision were a yearning to spend more time with grandsons, one-year-old Jackson and 18-month-old Charlie, and a sense of his own mortality, following a brush with skin cancer two years ago.

''Probably I'll remain clear of that, still am, but the spectre of that still hangs over you on a daily basis that at any time it can reoccur,'' he said.

''And so you do think about your future, your mortality, and what you want to do with the rest of your life.''

But the 52-year-old said it was colleague, former foreign minister, Alexander Downer's decision to depart that prompted him to go.

''While I was in serious contemplation of stepping down myself it's obviously sensible and economical to run two by-elections together.''

Nationals leader Warren Truss paid tribute to Mr Vaile for his contribution to the party and Parliament during which he became one of the world's longest-serving trade ministers.

''He was committed to freer and fairer trade and played a key role in some of the most significant trade negotiations of the modern era,'' Mr Truss said.

A number of Howard government high-flyers have quit politics in recent months, with Mr Downer announcing his departure last month and former agriculture minister Peter McGauran giving it away in April.

Mr Vaile would not comment on whether his former cabinet colleagues should call it a day soon.

NSW Labor Senator Mark Arbib said Mr Vaile's retirement was another example of the Coalition's contempt for voters.

''I think it's obscene that these three Coalition MPs stood in the last election and have left so soon,'' Senator Arbib said.

''Worse still, if all three Coalition MPs had have resigned at the same time it would have saved tax payers up to $1 million.''

Senator Arbib said former treasurer Peter Costello, former attorney-general Philip Ruddock, former immigration minister Kevin Andrews and backbencher Bronwyn Bishop should reveal whether they planned to quit immediately to enable subsequent by-elections to be held simultaneously.

''If that is their plan, then go now,'' he said.

''It's up to Brendan Nelson to show some leadership and ensure that happens.''

A spokesman for Dr Nelson, who is on leave, said the decision about Mr Costello's future was a matter for him.

Mr Vaile took the Nationals' leadership and deputy prime ministership in 2005 following the resignation of former leader John Anderson.

He stepped down as party leader following the Coalition's loss at the November 2007 election, in which he suffered a 5.2 per cent swing against him in his NSW mid-north coast electorate of Lyne.

Mr Vaile came under widespread criticism earlier this year for moonlighting for Sydney-based firm ServCorp in Dubai while still serving as an MP.

He wants to re-enter the property industry and would consider overseas work in trade and aid in developing countries.

He was elected as Lyne MP in 1993 and served in the Coalition's cabinet for more than 10 years as minister for agriculture, fisheries and forestry, transport and regional services and trade.

AAP