The UK must consider introducing conscription - and prepare for war with Russia, according to retired top British Army officer.

General Sir Richard Shirreff, a former NATO commander, joined growing calls for the UK to look at re-introducing conscription which would mean all young people are required to spend a period in military service.

He said: “Where is the mobilising of the defence industries, the mobilising of the national economy to fight a war? This is big stuff. This is really serious."

He spoke out after it emerged the UK is set to take in a peacekeeping force in Ukraine involving around 30,000 European troops. Downing Street has not confirmed the reports but Defence Secretary John Healey said the UK is “ready to play a full part ” in whatever “security guarantees” were needed to ensure a peace agreement lasts.

Sir Richard, who served as Deputy Supreme Allied Commander Europe, told the i newspaper: “I think that you’re going to be really pushed to do anything with 30,000.

“You’ve got to say, right, this is the nature of the task. This is what is required to do the task. Rather than saying the most we can provide is 30,000 and therefore, let’s find ways to make it stretch. So I don’t think it sounds credible, frankly.”

He said the UK should consider conscription to boost the size of the British Army to 100,000 with training to prepare Armed Forces reservists in the event of the “worst case”.

National service ended in the UK in 1960. Compulsory military service is in force in some form in nine European countries including Cyprus, Greece, Austria, Lithuania, Latvia, Estonia, Finland, Sweden, and Denmark.

A security conference in Munich last week would go down in history as marking the start of the betrayal of Ukraine he said, comparing it to the 1938 Munich conference which was supposed to secure peace but paved the way for World War II,

He said: “Munich, 1938 was a betrayal of Czechoslovakia, but at least it forced Chamberlain to kick off rearmaments.

“Munich 2025 is set to be a betrayal of Ukraine. But it should also be firing a starting gun to prepare Britain and Nato for war with Russia, because that ultimately is the only way we are going to maintain peace.”

There have been cross-party calls for a return to conscription or national service as the prospect of UK troops entering Ukraine looms.

Ex-MP Tobias Ellwood, former chair of the Commons defence committee, said the world was “getting more dangerous”. He said: “That’s why I’ve actually called for a return of national service. We’ve got an era of insecurity.”

Labour MP Paulette Hamilton told Channel 5’s Jeremy Vine show that young people could “no longer bury their hands in the sand” as “our borders are being threatened”.

She said: “I do think we need to start the serious discussions around conscription.”

Former Chancellor George Osborne said Sir Keir faced “one of the biggest calls” of his premiership and could find himself leading “a wartime government.”