LONDON, England (CNN) -- British Prime Minister Tony Blair has suffered his first major parliamentary defeat, losing a key vote on new anti-terror laws.The House of Commons voted 322 to 291 against a measure to allow authorities to hold terror suspects for up to 90 days without charge -- an increase from the current 14 days.It was the first major vote against the government since Blair and his Labour Party came to power in May 1997.CNN's European Political Editor Robin Oakley said Blair had invested his full political weight in getting the law passed, adding to the political drama.A tense Blair was in the chamber to hear the result, shaking his head as the numbers were revealed. Blair was uncontrite following the defeat, saying he brought the bill to the Commons because police had said they needed the longer detention period. "It was better to lose doing the right thing, than to win doing the wrong thing," he added.The prime minister had earlier made an impassioned plea for a "yes" vote."We are not living in a police state ... but we are living in a country that faces a real and serious threat of terrorism," he told the Commons.At least 41 members of his own party joined the opposition in Britain's lower house of parliament to reject the measure.The Commons later approved an amended measure to allow suspects to be held for up to 28 days without charge, but that may yet face a challenge.Defeat was a humiliating blow to the prime minister, and CNN's Oakley said it raised serious questions about his grip on power. Opposition leader Michael Howard said Blair, who has said he will not fight another general election, should now consider resigning as prime minister.Howard, leader of the Conservative Party, said Blair's authority was "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 terrorism bill was drafted following the July 7 suicide bombings on London's transport system that killed 52 commuters and the four suspected bombers, and failed attacks two weeks later.Designed to tackle Islamic extremism, the bill aimed to outlaw training in terrorist camps, encouraging acts of violence and glorifying terrorism.Many lawmakers feared a glorification clause could criminalize people supporting independence movements around the world.But police and prosecutors argued more time was needed in complex cases in which suspects often have multiple aliases and store information on mobile phones and on encrypted computers, and in which cooperation of foreign agencies was needed.Critics claimed holding people for three months without charge would erode civil rights.But Blair refused to back down and made the issue political, claiming the opposition Conservatives -- long regarded as the natural champions of law and order -- were soft on terrorism.During stormy exchanges at Prime Minister's Questions earlier Wednesday, Blair urged MPs of all parties to be "responsible" in backing the measures put forward by police."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."His resolve was stiffened by the belief that a majority of Britons supported the measure.Copyright 2005 CNN. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed. Associated Press contributed to this report.