London ? In a political blow to Prime Minister Tony Blair, British lawmakers on Wednesday rejected tough anti-terrorism legislation that would have allowed suspects to be detained for 90 days without charge.

The House of Commons vote was the first major defeat of Blair’s premiership and raises serious questions about his grip on power. Blair had staked his authority on the measure and doggedly refused to compromise.

Lawmakers, including 49 members of Blair’s Labour Party, opted instead for a maximum detention period for terror suspects of 28 days without charge.

Michael Howard, leader of the opposition Conservative Party, said Blair’s authority had “diminished almost to vanishing point” and said he should consider resigning.

“This vote shows he is no longer able to carry his own party with him. He must now consider his position,” Howard said.

But Blair was defiant. He ruled out resignation and insisted lawmakers had been wrong to put the civil liberties of a small number of terrorists ahead of the “fundamental civil liberty of this country to protection from terrorism.”

“The country will think that Parliament has behaved in a deeply irresponsible way today,” he added.

Lawmakers voted 322 to 291 against 90-day detentions and backed the 28-day period by 323-290 votes.

The result is a humiliating blow to Blair. For eight years, his Labour government commanded an unassailable lead in the Commons and easily swatted aside opposition to its legislation.

But Blair’s popularity has slumped in the wake of the divisive Iraq war, and his party was punished in national elections earlier this year. Labour’s huge 161-seat advantage in the Commons shrank to just 66, making the government vulnerable.

In the immediate aftermath of the July attacks on London’s transit system, Blair had considerable cross-party support for new anti-terror legislation.

He drafted the Terrorism Bill, which aims to tackle Muslim extremism by outlawing training in terrorist camps as well as encouraging acts of violence and glorifying terrorism.