Ben Wallace has confirmed he plans to resign at the next Cabinet reshuffle and will not seek re-election as an MP after four years as Defence Secretary.
He told The Sunday Times he will stand down but ruled out leaving "prematurely" and triggering another by-election for the Conservatives to battle.
Mr Wallace, who survived three prime ministers as Defence Secretary, played a key role in the UK’s response to Russia’s invasion of Ukraine and was a close ally of Boris Johnson.
His Wyre and Preston North constituency will disappear at the next election after boundary changes and he said he would not seek a new seat.
"I went into politics in the Scottish Parliament in 1999.
"That’s 24 years. I’ve spent well over seven years with three phones by my bed," he told the paper.
Mr Wallace had expressed an interest in standing for the role of Nato secretary-general before it was announced the current chief, Jens Stoltenberg, had been given another year in charge.
The minister told The Economist there were a "lot of unresolved issues" in the military alliance and "it’s not going to happen," and he later downplayed the prospect of a future bid to run the organisation.
Last week, the Prime Minister shut down comments from Mr Wallace in which he suggested Ukraine should show "gratitude" for the military support it has been given.
Mr Wallace had made the remark after the country’s president, Volodymyr Zelensky, branded it "absurd" for Nato to insist there were still conditions for his nation to meet before it can gain membership once the war with Russia is over.
Mr Zelensky later said: "I believe that we were always grateful to the United Kingdom.
"I don’t know what he meant and how else we should be grateful."
He took over from Penny Mordaunt as Defence Secretary in 2019, his former military career making him well-liked with many serving personnel.
Mr Wallace attended the Royal Military Academy Sandhurst and was commissioned into the British Army's Scots Guards at the age of 20.
During the 1990s, served in Northern Ireland, Germany, Cyprus and Central America.
In 1992, he was mentioned in dispatches.
Having entered politics as a Member of the Scottish Parliament in 1999, he was elected to the UK Houses of Parliament in 2005.
[Forces.net]