Britain scrapped national service for all young men in 1960, and occasional calls for its return have been confined to right-wing politicians and media.

Wallace, a former army officer, was briefing reporters alongside Swedish Defence Minister Pal Jonson about Sweden and Finland's bids to join NATO after Russia invaded Ukraine.

He conceded that "a different cultural thing" was at play after both Nordic countries persisted with conscription in the decades since World War II, albeit with a seven-year break for Sweden.

But Wallace said: "I think we're all envious of both Sweden and Finland, in (their) reserves."

He said reservists were especially important given the reliance of modern armed forces on specialists, for example in cyberwarfare, who could be activated in time of need.

"And I think we've got to recognise that again the lesson of Ukraine is how do we work on our resilience, and part of that is about reserves," he said.

"I would love to have a model like that."