“For that reason, I think it is sensible we take this decision today,” he added.  He contended that Britain would undermine its ability to press for disarmament if it scrapped its nuclear arsenal — the smallest among the five permanent members of the United Nations Security Council. “There is absolutely no evidence whatever that if Britain now renounced its independent nuclear deterrent that would improve the prospects of getting multilateral disarmament,” he said. “I think the reverse is the case.”  Traditionally, Labor has displayed a deep vein of antiwar and antinuclear sentiment and was formally committed to unilateral nuclear disarmament for many years.  Hundreds of people protested outside Parliament as lawmakers voted. On the London subway on Wednesday, antinuclear protesters handed out leaflets while wearing T-shirts proclaiming, “Tony loves W.M.D.,” the initials for weapons of mass destruction. Some church leaders joined a demonstration at a naval base in Scotland, where the Vanguard-class submarines that carry the nuclear missiles are based.  “In my judgment the U.K.’s continued possession of nuclear weapons is no longer simply maintaining the ‘balance of terror,’ but fueling the development of new nuclear weapons systems around the world,” Patrick O’Donoghue, the Roman Catholic bishop of Lancaster, said in a statement.  The foreign secretary, Margaret Beckett, told lawmakers before Wednesday’s vote that Britain would cut its arsenal of nuclear weapons by 20 percent this year, to fewer than 160, which would be a 75 percent reduction since the end of the cold war. Britain’s four Vanguard-class submarines each carry 16 American-supplied Trident long-range missiles with British nuclear warheads. They are supposed to maintain permanent patrols around the globe. Both Mr. Blair and his likely successor, Gordon Brown, say Britain should embark on building a second generation of submarines because the present vessels will go out of service by 2024 and it will take 17 years to design and build replacements.  The Labor Party has a majority of over 60 among the 646 members of the lower House of Commons.  Mr. Blair has faced rebellions in the past, notably among the nearly 140 Labor lawmakers who opposed the invasion of Iraq. He won that vote in March 2003, when the opposition Conservatives voted in favor of the invasion. But he lost a vote on an antiterrorism measure in November 2005 — the first such defeat since Labor won power in 1997.  In Wednesday’s ballot, legislators cast votes for two measures. The first, which the government opposed, said that there was no need yet to decide on the renewal of the nuclear deterrent. Mr. Blair won defeat of that motion, 413 to 167, with others absent or abstaining, meaning that roughly 90 Labor legislators had broken ranks with his party, some had abstained and many of the almost 200 Conservatives had voted with Labor.  The second was a straight vote on whether the nuclear submarine fleet should be renewed. Mr. Blair won that vote by 409 to 161, with a rebellion of around 85 Labor legislators.  Earlier the Conservative opposition leader, David Cameron, pledged to support the government in renewing the submarine program — a policy the Conservatives have long supported. By depicting Mr. Blair as reliant on Conservatives, the opposition seeks to highlight what it calls weakness on the part of Mr. Blair.  A version of this article appears in print on , on Page A8 of the New York edition with the headline: Blair Wins Vote to Renew Atom Arsenal. Order Reprints| Today's Paper|Subscribe
Prime Minister Tony Blair faced down a mutiny in Parliament, winning a vote to renew Britain’s nuclear deterrent.