The British Army would be destroyed in “six months to a year” if it had to fight Russia, the veterans minister has warned.

Colonel Alistair Carns, a former marine and current reservist, said it would not be possible for the UK to sustain losses like those suffered by the Kremlin’s forces – estimated at 1,500 troops per day in Ukraine – in the event of a war.

Speaking at a conference on reserves, he said: “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 multi-national coalition, in six months to a year.”

The British Army currently has 72,510 full-time troops – its smallest size since the Napoleonic era.

However, Col Carns said: “That doesn’t mean we need a bigger army, but it does mean you need 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.”