The Government last night survived a major Labour backbench revolt to secure the backing of the House of Commons for its plan to replace Britain's Trident nuclear deterrent.
The Government won the main motion by 409 votes to 161. Earlier, an amendment tabled by rebel Labour MPs to delay Trident renewal was defeated by 413 to 167.
More than 90 Labour MPs voted for delay, with others abstaining, making it the biggest revolt since the Iraq war.
With David Cameron's Tories voting for Trident replacement the Government was never in danger of defeat.
However the scale of the rebellion is another blow for the authority of Tony Blair.
Earlier two more ministerial aides - Stephen Pound, the parliamentary private secretary to Labour Party chairman Hazel Blears, and Chris Ruane, the PPS to Northern Ireland Secretary Peter Hain - resigned in protest.
In the Commons, Mr Blair defended the decision to retain Trident and said it was essential a decision to begin work on designing a new submarine fleet was taken now.
"I think that is essential for our security in an uncertain world," he told MPs at Prime Minister's Questions. "We can't put this decision off. We have to take it now."
In an olive branch to opponents of Trident renewal, Mr Blair said future Parliaments would be able to revisit the issue as the actual orders for the submarines would be placed early in the next decade.
Mr Cameron also emphasised his party's support for maintaining Trident. "Replacing Britain's independent nuclear deterrent is in the national interest," he said. "In a dangerous and uncertain world, unilateral nuclear disarmament has never been and will never be the right answer."
However, Liberal Democrat leader Sir Menzies Campbell, arguing for delay, warned that a "hasty" decision on Trident renewal would undermine Britain's influence at forthcoming nuclear non-proliferation's talks.
Opening the debate, Foreign Secretary Margaret Beckett, said Britain could not afford to unilaterally disarm at a time when other countries were acquiring nuclear weapons.
"To decide not to retain that ability would require us to be confident that in the next 20 to 50 years no country with a current nuclear capability would change its intentions towards us and that no power hostile to our vital national interests and in possession of nuclear weapons would emerge."
She said that with the existing submarine fleet coming to the end of its life from 2022, and 17 years needed to design and build replacements, decisions were needed now.
Nigel Griffiths, who resigned as Deputy Leader of the Commons in protest at Trident renewal, said he was voting against the Government with "a heavy heart but a clear conscience".
Labour left winger John McDonnell, who intends to challenge Chancellor Gordon Brown for the Labour leadership when Mr Blair steps down, warned that the campaign against Trident renewal would continue.