Ben Wallace, British Defence Minister, has said he will not stand as an MP in the next general election.
Mr Wallace will step down from his position and leave the cabinet when Prime Minister Rishi Sunak carries out his next reshuffle, he told The Times newspaper on Saturday.
“I’m not standing next time,” Mr Wallace said.
He also ruled out forcing a by-election by leaving Parliament before the next election, which must be held before the end of January 2025.
“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 said.
“I took over a department that had suffered 30 years of cuts and conceded that the whole of government was about health and education, while defence was just a discretionary spend.
“What I hope I’ve managed to do the last four years is unlock genuinely new money and win the argument that defence is core.”
Mr Sunak was told in mid-June and the decision was made public on Saturday.
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 is an ally of Boris Johnson.
He is the longest continuously serving minister in Government, having been security minister under Theresa May before being promoted to defence chief by Mr Johnson.
Mr Wallace, 53, was an early frontrunner in the race to replace Mr Johnson but ruled himself out of the running.
Last week, he attracted headlines at a press conference when he said the UK was not an “Amazon” delivery service for weapons to Ukraine and that Kyiv might be wise to let its supporters “see gratitude”.
He has served as Conservative MP for Wyre and Preston North and its predecessor constituency in north-west England since 2005.
The seat in Lancashire is to be abolished at the next election under boundary changes.
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.
He 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 later bid to run the organisation.
He trained as a cadet at Sandhurst military academy and rose through the Army's ranks to become a captain in the Scots Guards.