Tony Blair was facing backbench calls to stand aside after nearly 63 Labour MPs inflicted a first, and overwhelming, Commons defeat on his eight-year-old government, spurning his personal plea to respect the police by giving them powers to detain terrorist suspects for up to 90 days.

In the biggest reverse for a government on a whipped vote since James Callaghan's administration, Mr Blair was defeated comprehensively by 322 to 291, with 49 Labour backbenchers, including 11 former ministers, defying a three-line whip. Thirteen others abstained.

As the impact on the prime minister's authority sunk in, MPs then voted by 323 to 290 to support detention without charge for only 28 days, the position advocated by the Liberal Democrats and the Tories. The scale of the defeat rocked Labour whips, raising questions about Mr Blair's political judgment of late and suggesting that he now has a permanent cadre of irreconcilable backbenchers who neither listen to nor respect his views, leaving him in charge of an effective minority administration on controversial issues.
The former cabinet minister Clare Short said the defeat presaged further revolts. "It would be good for him, and certainly the Labour administration, if he moved on quickly," she said. Another former minister, Frank Dobson, predicted bigger revolts on Mr Blair's plans for schools.

Cabinet ministers insisted they would not water down their reform programme, but they will have to redouble their efforts to explain their plans on education, incapacity benefit and health reform.

Mr Blair, who personally decided to gamble by putting the 90-day detention to the vote, sounded an uncomprehending note afterwards. "The country will think parliament will have behaved in a deeply irresponsibly way, I have no doubt about that at all," he said. "Sometimes it is better to do the right thing and lose, than to win doing the wrong thing. I have no doubt what the right thing was to do in this instance, to support the police.

"When the police say they are fighting mass-casualty terrorism and they provide examples of why they need the powers, I think you need powerful reasons to turn round and say no to them." He added: "There was every possible safeguard, with the police having come back to a high court judge to make its case every seven days".

He said he would not try to overturn last night's vote. "Parliament cannot be treated like children, they know what the issues are."

Rejecting the notion of turning the reverse into a vote of confidence, the prime minister again promised to serve a full term, adding that his main domestic reform bills were unaffected. "In this business you get knocks the whole time. Wait and see what happens with the main government programme, because I think that is completely different. I don't think we will be defeated on those issues. This was an issue on its own."

Michael Howard, the Conservative leader, said: "Mr Blair has been engaged in the most appaling distortion of the arguments. Mr Blair's authority has been diminished almost to vanishing point. This vote shows he is no longer able to carry his own party with him. He must now consider his position." The Liberal Democrat leader, Charles Kennedy, said the prime minister had to learn he needed to build consensus.

Mr Blair's majority vanished even though the chief whip, Hilary Armstrong, sent out a midnight SOS to the chancellor, Gordon Brown, and the foreign secretary, Jack Straw, to return from important overseas visits to vote in the Commons and sway colleagues. The party chairman, Ian McCartney, limped in from his hospital bed after a triple heart bypass operation.

Even though Mr Brown, due to meet the Israeli prime minister yesterday, flew back in the morning after less than an hour in Israel, he was unable to hold back the avalanche. Few of his allies were taking pleasure in the outcome, aware that they want the chancellor to inherit a united party.

The whips were taking some blame for signally misreading the mood of the party after Mr Blair won accolades for a bravura performance at a private meeting with Labour MPs. Others said it had been Downing Street and not the home secretary, Charles Clarke, that had made the judgment call to go for broke with a vote on 90 days. Both the Home Office and the prime minister denied a split on tactics.

At an electric prime minister's questions, an angry Mr Blair tried to discomfort the Tories. "When those charged with protecting our country provide, as they have, a compelling case for action, I know what my duty is. My duty is to support them, and so is the duty, in my view, of every member of this house." At one point, Mr Blair looked about to lose his temper when one Tory shouted that he was trying to set up a police state.

Mr Howard defended a position that has caused fissures in his own party, saying: "We all want to fight terrorism effectively. But you don't have to look very far beyond our shores to see what happens if you alienate minority communities."

Mr Blair's position weakened during the day when he discovered that the nine Democratic Unionist MPs were going to vote against the government, angry at a separate bill published yesterday giving an amnesty for terrorist on the run in Northern Ireland. The forecast revolt of Conservative dissidents evaporated, leaving Mr Blair hoping that his basic appeal to loyalty would save him. But the rebellion spread beyond the usual suspects.

Many Labour rebels, including five new intake members, were angry, claiming that Charles Clarke, the home secretary, had betrayed them last week when he persuaded rebels to pull a vote by promising to come back with new proposals based on a consensus. Mr Dobson said: "I think the police asked for three months thinking they would get six weeks, and if the government had kept its promise and come up with a compromise, that vote might have gone through."

Ian Paisley, the DUP leader, was more blunt: "Blair's authority has gone. He should have a 60-odd majority, he has lost that. In no way could you put any sugar on that cake. Indeed, it isn't even a cake. It is a crust."