Tony Blair says his authority is intact despite suffering his first House of Commons defeat as prime minister.
He said he hoped MPs "do not rue the day" they rejected his call to allow police to detain terror suspects for up to 90 days without charging them.
MPs voted against by 322 votes to 291, with 49 Labour MPs rebelling, but later backed a proposal to extend the detention time limit to 28 days.
Conservative leader Michael Howard said Mr Blair should resign.
Lib Dem leader Charles Kennedy warned Mr Blair could become a "lame duck" leader.
Following the defeat MPs backed by 323 to 290 votes a Labour backbench MP's proposal to extend the detention time limit to 28 days, from the current 14 days.
Mr Blair, who is planning to quit as prime minister before the next election, has said he will serve a full third term.
But Mr Howard said the vote had "so diminished" Mr Blair's authority that he should quit now.
And Lib Dem leader Charles Kennedy said Mr Blair would be seen as a "lame duck" leader unless he realised he could not behave in a "quasi-dictatorial way".
"If he doesn't, then increasingly his premiership is becoming a John Major premiership, at the mercy of events, at the mercy of opposition, not just from other political parties but from within his own," said Mr Kennedy.
But Mr Blair told the BBC he did not believe the vote would affect his position as prime minister.
"I don't think it is a matter of my authority - of course I would have preferred to have won rather than lost," he said.
90 days' detention time limit: Defeated by 322 votes to 291, majority 31
Backbench compromise of 28 days' detention: Passed by 323 votes to 290, majority 33
He said the police had told him the case for the 90-day detention proposal was "vital" and "compelling".
It had been his duty to put the plan before MPs and it had been their right to vote against it, he said.
But, he said: "I think it was a wrong decision - I just hope in a longer time we don't rue it."
He said people would think it was "very odd" that given the advice of the police and security services, MPs had "decided to ignore their recommendation".
Instead they had voted for a 28-day detention limit which "they have thought of themselves" without any particular justification, he said.
Home Secretary Charles Clarke said he had not suspected until half an hour before the crucial vote that the government might lose.
But he said the prime minister had not been "foolhardy" in pressing for the 90-day plan - and the defeat would make him want to go on longer in the job rather than quit.
"He's feeling angry that this important proposal for the security of the nation was not carried by Parliament and cross at our failure, my failure, to actually get across to all of our parliamentarians the scale of the issues involved," he said.
And the idea that the defeat had weakened Mr Blair's position was "quite wrong" because the proposals were not "at the core" of the government's counter-terrorism plans, he added.
'No police state'
Shami Chakrabarti, director of the civil rights group Liberty, said she was "heartened" that MPs had defeated the 90-day plan.
In his final plea for MPs to back the plans, Mr Blair urged MPs to take the advice of the police who had foiled two terrorist plots since the 7 July attacks in London.
In heated exchanges at prime minister's questions, Mr Blair said: "We are not living in a police state but we are living in a country that faces a real and serious threat of terrorism."
Ministers had tried to reassure wavering Labour MPs by promising that the new laws would expire unless the Commons renewed them in a year's time.
Other concessions included promising scrutiny of the detention process by a High Court judge.
In a sign of the importance given to the vote, Chancellor Gordon Brown was called back within minutes of arriving in Israel for a high profile visit.
And Foreign Secretary Jack Straw also flew back early from EU-Russia talks in Moscow.
Later, in a separate vote, the government's majority was reduced to 25 when MPs backed the inclusion of "glorification of terrorism" in the Terrorism Bill.