Gordon Brown told the Conservatives they should "think again" on the case for an extension of the pre-charge detention limit for terror suspects to 42 days in today's prime minister's questions.
Tory leader David Cameron used all his six questions on 42-day detention issue, predicting a similar "U-turn" would be necessary over the issue as occurred with the 10p tax rate last week.
But Mr Brown responded by telling the Conservative party "it should be ashamed of itself [by] not supporting this legislation" and argued the government had dealt with civil liberty concerns affecting the problem.
The counterterrorism bill proposes raising the maximum limit for terror suspects' pre-charge detention from the current 28 days to 42 days, but only after the home secretary has come before the Commons.
After trading lists of those who had disagreed or agreed with the government's stance on the issue, Mr Cameron and Mr Brown turned on each other's leadership style along the usual lines.
Mr Cameron continued last week's argument that the prime minister was motivated more by spin than a desire to do good for Britain.
"He puts political calculation and self-interest ahead of the right decisions and the national interest," he said, raising the first cheers of the session.
The prime minister hit back, however, with a sustained attack against Mr Cameron.
"Once again, he never addresses the substance of the question," Mr Brown said.
"This is the man who wants to both tough on crime and hug a hoodie at the same time," he continued.
"This is the man where political calculation meant he cycled to work but at the same time had a chauffeur-driven car coming behind.
"This is the man who is a shallow salesman and never addresses the substance of the issue."
Liberal Democrat leader Nick Clegg concentrated his attack on the government's record for low-earners, asking why any low-earner should vote for Labour in tomorrow's local elections.
Mr Brown responded by citing the New Deal, raised child tax credits and child benefit and the million pensioners who have been raised out of poverty since 1997.
"The reason people should support Labour is because our policies for social labour are not only taking people out of poverty but helping them into work," he added.