Tony Blair was accused of stretching Britain's armed forces to breaking point to serve his "global ambitions".
Conservatives went on the offensive, warning that the Prime Minister's moves to increase peace-keeping and other operations overseas were forcing the cancellation of vital training and driving personnel out of the services.
The former Tory defence secretary Lord King raised concerns about Britain's overseas commitments during a debate in the House of Lords.
Bernard Jenkin, the shadow Defence Secretary, also said an unsustainable burden was being imposed on the armed forces. "If we are going to use the armed forces for a much wider nation-building role, then you have to up the ante," he told BBC Radio 4. "It is either the Prime Minister's global ambitions or the Treasury, but you can't carry on indefinitely overstretching the armed forces in this way."
Lord King told peers he was "extremely concerned" that 85 training exercises had been cancelled last year. "If we are going to have good forces, they must be well trained," he said.
"We simply will not be able to point to the priceless asset that is at present our armed forces, cherished by all parties in this house, unless we ensure that our forces are properly trained, get proper rest and recreation and time with their families, and then they will be able to make the commitment that is an essential part of the role that we look to them to play."
Mr Jenkin said that even though troop numbers had fallen by 10,000 since 1997, the Army was now taking part in more deployments. "It is too early to say what money [the Tories] are going to spend on defence," he said. "We are years away from a general election. But the question is, do you carry on this much wider peace-keeping, nation-building deployments?"
Geoff Hoon, the Secretary of State for Defence, insisted that current deployments were in line with 1997 levels. "I am confident we can do the job or we would not have undertaken it," he said. "It is vitally important that we assist in rebuilding Afghanistan to avoid the kind of catastrophe that the world suffered on 11 September."Reuse content