Ben Wallace to quit as MP at next general election | Ben Wallace

Ben Wallace is to leave government at the next cabinet reshuffle after four years as defence secretary and will not stand in the general election.

Wallace, who has played a key role in responding to Russia’s invasion of Ukraine and was a close ally of Boris Johnson, told the Sunday Times he was “not standing next time” but he ruled out leaving parliament “prematurely” and forcing another byelection on Rishi Sunak, of whom he remains supportive.

His departure is not related to the Conservative party’s current challenges, according to multiple reports.

“I went into politics in the Scottish parliament in 1999,” he told the paper. “That’s 24 years. I’ve spent well over seven years with three phones by my bed.”

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 his getting the job was “not going to happen”. He later downplayed the prospect of a future bid to run the organisation.

Last week, the prime minister shut down comments from Wallace in which he suggested Ukraine should show “gratitude” for the military support it had been given.

Wallace had made the remark after the country’s president, Volodymyr Zelenskiy, said it was “absurd” for Nato to insist there were still conditions for Ukraine to meet before it can gain membership once the war with Russia is over.

Zelenskiy later said: “I believe that we were always grateful to United Kingdom. I don’t know what he meant and how else we should be grateful.”

Popular within the Tory party, Wallace is the longest continuously serving minister in government, having been security minister under Theresa May before being promoted to defence secretary by Johnson and continuing the role under his two successors.

He was previously appointed as a whip in 2014 and a junior minister in the Northern Ireland Office in 2015 while David Cameron was prime minister.

The Wyre and Preston North MP ruled himself out of the running for the Conservative leadership last year, despite being an early frontrunner in the race to replace Mr Johnson.