Tony Blair has conceded he will have to compromise on his own will on plans to allow terror suspects to be held for up to 90 days without charge.
The prime minister blamed the Conservatives and his own MPs for forcing him into dropping the proposal from his Terrorism Bill being debated this week.
Speaking at his monthly press conference in Downing Street on Monday, he said the climb down will be a "compromise for this nation's security".
Maintaining that he still hopes to persuade parliament to accept the police's request for a 90-day limit, Blair defended the proposal as a "compelling" case and denied it had been "dreamed up by me".
"The challenge of this type of terrorism it not one that can be met by the policing methods of the 1990s," he said.
He also argued it was "wrong to frame this debate simply in terms of the civil liberties of terrorist suspects".
"Of course their liberties are important, but so are the liberties of the people who may be victims of a terrorist attack," Blair told reporters.
"What about their most basic civil liberty, their right to life?"
But acknowledging that amendments to the Bill would be tabled in order to lower the limit in the legislation, he slammed his opponents and his own MPs.
He said their stance was taken "on the basis that they know better" than the police.
"If we are forced to compromise, it will be a compromise for this nation's security," the prime minister insisted.
He asked why "the Conservative Party, en masse, including its two leadership candidates who claim they want to be prime minister of this country" were opposing the advice of the police and security services.
But he resisted making the cause a matter of confidence in the Commons in order to flush out Labour rebels, claiming the idea would be a "distraction" and give "Conservatives and Lib Dems a reason to get off the hook".
Blair claimed he had looked senior police officers "in the eye" last week in a discussion on the issue.
"They are not saying it in a 'this would be quite nice to have' kind of way," he said.
"They said to me - and the word that they used - is that it is 'compelling'."
No consensus
Earlier home secretary Charles Clarke met representatives of the opposition parties in a further bid to achieve a consensus on the response to the July 7 attacks on London.
They failed to reach a deal on the detention limit, with the Conservative suggestion of 28 days as an absolute maximum being rejected as "unacceptable" by Clarke.
However he refused to commit to a figure between 28 and 90 days ahead of tabling an amendment later in the day.
"We do not accept that 28 days is an appropriate period," Clarke said.
"Later today I will be tabling an amendment to reduce the amount of time from 90 days, but not as low as 28 days.
"We are going to continue our conversations with backbench members of parliament on all sides of the House, because there are a number of Conservatives and others, as well as people on the Labour side of the House, who believe that an amount of time greater than 28 and less than 90 is right."
Shadow attorney general Dominic Grieve agreed that "we remain apart in respect of duration".
"The government has not as yet come up with any figure on the duration of detention other than 90 days," the Conservative said.
"And the ball is therefore firmly in the government's court to make up its mind what it wants to do about that.
"We have made clear that 90 days is totally unacceptable and I think that is the universal view by those who attended this meeting, other than the government ministers.
"But we are prepared to continue talking to the government about other possibilities."
