Major war could destroy UK army in six months – minister Alistair Carns

“In a war of scale – not a limited intervention, but one similar to Ukraine – our army for example on the current casualty rates would be expended, as part of a broader multinational coalition, in six months to a year,” he added.

In a speech on reserves at the Royal United Services Institute defence think tank, external in London, Carns, the minister for veterans and people, said: “That doesn’t mean to say we need a bigger army, but it does mean we must be able to generate depth and mass rapidly in the event of a crisis.

“The reserves are critical, absolutely central, to that process.

“Without them we cannot generate mass, we cannot meet the plethora of defence tasks and challenges that we require, and we cannot seamlessly integrate the very best experts into the heart of our armed forces.”

Army reservists serve in their spare time, getting paid to train outside their main jobs.

Carns said the reality of wars such as the one being fought in Ukraine was that they were “attritional in nature”.

He also said the UK needed to “catch up with Nato allies” by placing a greater emphasis on its reserves.

The prime minister’s official spokesman said Defence Secretary John Healey had already spoken about “the state of the armed forces that were inherited from the previous government”.

“It’s why the Budget invested billions of pounds into defence, it’s why we’re undertaking a strategic defence review to ensure that we have the capabilities and the investment needed to defend this country,” they added.