The former foreign secretary Sir Malcolm Rifkind says the government should not pay for the war in Afghanistan out of the core defence budget.
Interviewed by Today presenter Sarah Montague, Sir Malcolm said that he welcomed the provision of more equipment for Afghanistan but added that he was "very deeply disturbed" that the money might come from the core defence budget, rather than from a contingency fund. He said this had "ominous implications for the integrity of our armed forces".
And he called for an immediate review of the UK's defence and foreign policy which would involve opposition parties.
Bob Ainsworth, the Defence Secretary, is set to outline government plans to pay for extra equipment for British operations in Afghanistan by making cuts elsewhere.
He is expected to tell MPs more than 20 Chinook helicopters are being ordered over the next 10 years. The BBC understands that parts of RAF Kinloss in Scotland may be mothballed as part of the cuts and there are fears that thousands of defence jobs could be lost Whitehall and also within the armed forces.