The defence review completed last autumn should be reopened in the wake of the Libya crisis, says senior Conservative MP David Davis.
The ex-shadow Home Secretary, said: "The real truth here is that this review has not met the test of time even over six months. So it's not going to meet it over the course of 10 years."
Labour has joined ex-service chiefs in proposing a rethink on the Strategic Defence and Security Review, the first such exercise since 1998, and Mr Davis's intervention will increase pressure on ministers to think again.
"There are lots of errors of assumption in it, and it simply isn't enough to maintain the role that we want for ourselves," he told The Independent's Mary Ann Sieghart on Radio 4's Beyond Westminster.
The review did not forsee circumstances in which Britain would need a maritime coastal operational capability. "That was two, three months before Libya when we absolutely need maritime coastal capability," he said.
He rejected ministers' claims that a defence rethink would reopen the Government-wide spending review This . was "just arithmetic nonsense"
Although the Treasury may allow the MoD some flexibility so it can preserve some jets, frigates and transport aircraft, Defence Secretary Liam Fox has ruled out a new review.
Lord Guthrie, the former Chief of the Defence Staff, said: "You do need balanced forces. And the Army is taking the strain now rather more than the other two services. But you can cut too deeply." Warning that Libya is getting into a difficult stage, he told the programme: "Once you're in, it's sometimes very difficult to get out. And you shouldn't intervene where you haven't got much prospect of success."
He was suspicious of using air power alone. "I'm not quite sure what's going to help us now except diplomacy and political pressure which hasn't worked so far," he said, adding that if bombing continues, people can make mistakes. "You have to be very, very careful because the alliances one gets involved with are unlikely to hold together."