Ben Wallace is understood to be considering leaving Government in the autumn after four years as Defence Secretary.
The Times reported Mr Wallace, who has played a key role in responding to Russia’s invasion of Ukraine and was a close ally of Boris Johnson, is weighing up whether to exit politics entirely.
He remains supportive of Rishi Sunak and the Government and the departure would not be related to the Conservative Party’s current challenges, the paper reported.
The PA news agency understands Mr Wallace has not yet made a decision.
Mr Wallace’s potential departure comes ahead of an expected re-shuffle by the Prime Minister.
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”. 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 had 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 United Kingdom.
“I don’t know what he meant and how else we should be grateful.”
Popular within the Tory party, Mr Wallace is the longest continuously serving minister in Government, having been security minister under Theresa May before being promoted to Defence Secretary by Mr 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.
