Lib Dems accused of 'playing politics' over Trident
The Lib Dems have been accused of trying to score "political points" by delaying the replacement of Trident.
The final decision on the nuclear weapons could be delayed until after the 2015 election, defence minister Nick Harvey told the party.
He said this would have no financial or security implications - but would be a political "hot potato" for Labour.
Labour accused Mr Harvey of "immaturity" and threatening the national interest.
The Lib Dem conference voted for a full review of plans for a like-for-like replacement for the nuclear system.
It said the decision not to include Trident in the upcoming defence spending review was "untenable".
The cost of renewing the system is expected to be between £20bn and £30bn.
The Lib Dems oppose an identical replacement for Trident, arguing it was designed for the Cold War, but the Tories and Labour are strongly in favour of one.
In their coalition agreement, the Lib Dems and the Conservatives said they would carry out a study aimed at exploring cheaper options.
It also allows their respective MPs to vote differently on the issue, meaning the conference vote is largely a restatement of Lib Dem policy.
In July, Conservative Chancellor George Osborne said the cost of replacing Trident would have to come from the Ministry of Defence's budget, rather than directly from the Treasury.
Cambridge MP Julian Huppert, who proposed the emergency conference motion, said he wanted this policy to be looked at in more detail, with a full review rather than just a study.
He opened the debate by saying: "If it was up to me, I would scrap Trident today."
Mr Huppert added that the money could go on better body armour for troops serving in Afghanistan or improved housing and care for personnel and ex-personnel.
He said: "I say to the Tories that there's nothing to worry about. If it turns out that Trident is essential it will pass the review with flying colours. If it doesn't then it shows it really must be reviewed."
He wanted to "send a message to the Tories and give the Liberal Democrat Members of Parliament and ministers the support we need to press for this money [to be taken away from renewing Trident]".
Former cabinet minister Baroness Williams said Trident was a "Cold War" weapon which was no longer needed.
Armed forces minister Nick Harvey assured the conference that the Lib Dems would not support the Conservatives on Trident, pointing out that this difference was allowed under the coalition agreement.
But he said the "main gate" decision on the nuclear weapons system - the "point of no return" - is currently scheduled for the end of 2014 or the start of 2015 - and delaying for a few months until after the May 2015 would not make any financial or industrial difference.
"But believe me, it is of profound political significance," he added.
"Conservatives know that they are not going to be able to look to the Liberal Democrats to get that through Parliament, so the issue will be a hot potato for Labour."
Rather than branding the Lib Dems "crypto Tories," Labour would then have a "headache" over "whether they are going to ride to the rescue of the Conservative Party on Trident," he told activists.
The Lib Dems will not change their minds on replacing Trident but "as for Labour - watch this space," he added.
His comments prompted an angry reaction from Labour. Shadow Defence Secretary Bob Ainsworth MP said: "This is a completely immature way to decide our future defence and security policy.
"The government must make those decisions in the best interests of our country, not delay them just to score political points. Putting off difficult decisions shows just how weak this coalition is.
"The Liberal Democrats needs to grow up and start acting like a responsible governing party."
The motion, passed overwhelmingly on a show of hands, called for an extension of the defence spending review to cover Trident.
It suggested looking at "cost-saving options" such as ending continuous at-sea patrols and lengthening the operational lives of the Vanguard submarines used to carry nuclear missiles.
The motion also said the review should make it clear how much Trident replacement would cost in terms of cuts to troop numbers and equipment programmes.
Trident consists of four submarines that can deploy ballistic missiles carrying nuclear warheads.