The Liberal Democrats are to delay backing a specific alternative to Trident as they attempt to persuade Labour to join them in opposing a like-for-like replacement.

The party scored a significant victory when they secured a Government review into the options for the future of the UK's ageing nuclear deterrent. It is due to report next year, outlining a number of different outcomes for the UK's £25 billion Trident update programme.

Although the LibDems are expected to include a specific option in their 2015 manifesto, they will not immediately nail their colours to the mast.

Sources said it was felt they would be unwise to show their hand before a consensus could be built in the defence community and before they could convince Labour on to their side of the argument. A LibDem source said: "If both Labour and the Conservatives go into the next election promising a like-for-like alternative in their manifestos, it does not matter what the LibDems do."

Labour suggested the LibDems faced an uphill battle. A spokesman said: "It is for the LibDems to disprove Trident as it stands is not the most capable and cost-effective option."

The junior Coalition partners argue the current nuclear deterrent system is a costly way to deal with a conflict that no longer exists – the Cold War.

LibDems believe the public will be open to arguments that a like-for-like replacement would be too expensive. Nick Clegg warned it would involve spending "billions and billions and billions on a nuclear missile system with the sole strategic purpose of flattening Moscow at the press of a button."

His party is understood to be convinced of the need for an option that would see the system put on "standby" and able to be reactivated at short notice.

Both Government parties agreed to delay the so-called "main gate" decision on Trident until 2016, after the next General Election. At that stage the exact nature of the new system will have to be agreed.

Even before that call is made, however, the Ministry of Defence has announced hundreds of millions of pounds for design work. Labour's John Woodcock said "all the options" had been scrutinised in previous studies into alternatives to Trident.

These, he said, had "found that actually this idea that there is an off-the-shelf, cheaper version is a fallacy."

In Scotland the party has long accused the SNP of jeopardising thousands of Scottish jobs with its opposition to Trident.

The Tories argue the UK needs to maintain the UK's nuclear deterrent as it is.