The British Army would be wiped out in as little as six months if forced to fight a war on the scale of the Ukraine conflict, a defence minister has warned.

Alistair Carns said a rate of casualties similar to Russia’s invasion of Ukraine would lead to the army being “expended” within six to 12 months.

He said it illustrated the need to “generate depth and mass rapidly in the event of a crisis”.

In comments reported by Sky News, Mr Carns, a former Royal Marines colonel, said Russia was suffering losses of around 1,500 soldiers killed or injured a day.

“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,” Mr Carns said in a speech at a conference on reserves at the Royal United Services Institute defence think tank in London.

He added: “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.”

Official figures show the army had 109,245 personnel on October 1, including 25,814 volunteer reservists.

Mr Carns said: “The reserves are critical, absolutely central, to that process.

“Without them we cannot generate mass, we cannot meet the plethora of defence tasks.”

Mr Carns, the minister for veterans and people, said the UK needed to “catch up with Nato allies” to place a greater emphasis on the reserves.

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

The spokesman said: “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.”