Tony Blair suffered a massive blow to his authority last night as Labour rebels led by a Midland MP rejected anti-terror laws personally championed by the Prime Minister.
Plans to give police the power to hold terror suspects for 90 days without charge were rejected by the House of Commons, after Labour dissidents joined forces with Conservatives and Liberal Democrats.
MPs instead backed proposals from David Winnick (Lab Walsall North), usually a loyal Labour backbencher, limiting the time period allowed to 28 days.
Mr Blair's failure to win a Commons majority raises questions about his ability to push through controversial plans for schools and hospitals in the months to come.
Downing Street last night insisted the vote had been a "one off" because the topic was so controversial.
But former Cabinet Minister Clare Short, MP for Birmingham Ladywood, said the defeat could bring forward his departure as Labour leader.
She said: "I hope it speeds him on his way. It would be good for the country, for him, and certainly for the Labour Government."
And Conservative leader Michael Howard said: "This vote shows he is no longer able to carry his own party with him. He must now consider his position."
Labour has a Commons majority of 66, but MPs rejected the Government's proposal by 322 votes to 291. Minutes later they backed Mr Winnick's amendment by 323 to 290.
A tense-looking Mr Blair, in the chamber to hear the result of the first vote, shook his head as the numbers were revealed.
It means the period police can hold terrorist suspects before either releasing them or charging them has been doubled from 14 days to 28.
But Mr Blair had thrown his personal backing behind the Government's plans for a 90-day period, insisting police and security services needed far-reaching powers to combat terrorism.
Senior police officers including Sir Ian Blair, Commissioner of the Metropolitan Police, had backed the Government's line.
During stormy Commons exchanges with Mr Howard earlier in the day, Mr Blair told MPs: "We are living in a country that faces a real and serious threat of terrorism - terrorism that wants to destroy our way of life.
"When those charged with protecting our country provide, as they have, a compelling case for action, I know what my duty is."
As the Government battled to win over wavering backbenchers, Chancellor Gordon Brown and Foreign Secretary Jack Straw were ordered to cut short highprofile trips overseas in order to boost numbers backing the Government line.
Speaking after his victory, Mr Winnick said Mr Blair still had "full enthusiastic support" from the majority of Labour MPs had "full enthusiastic support" from the majority of Labour MPs and advised any plotters to "take a running jump".
In an interview after the vote, Mr Blair insisted he had done the right thing in putting the issue to Parliament. "I think people in the country will find it very odd that MPs, given such a strong and compelling case by the police, decided to ignore their recommendation and to go for a period they thought of themselves without any justification for it."