Liberal Democrats have demanded a review of plans to replace Trident, placing them in opposition to the Conservatives over the future of Britain’s independent nuclear deterrent.

Tories back replacing Trident with a similar system and have refused to include it in a strategic defence and security review they set up after taking power.

But Lib Dem members in Liverpool voted unanimously for a policy motion calling on ministers to allow a full review of alternatives to the like-for-like replacement.

Armed forces minister Nick Harvey gave delegates a strong hint that the final decision on Trident would take place after the 2015 general election – when the Lib Dems and Conservatives may not be in coalition any more.

He said: “If it were to be delayed until just after the May 2015 election, it is of no great financial significance, it is of no great military significance, it is of no great industrial significance.

“But believe me, it is of profound political significance. 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.”

Mr Harvey supported the motion, describing it as a “very useful restatement of our policy on this issue”.

Lib Dems believe the UK should not commit itself to “another Cold War-scale nuclear deterrent and take up that stance for another 40 years”, he said.