POLITICIANS are at loggerheads over the future of the UK's nuclear deterrent system.

A review of Trident ordered by Liberal Democrat minister Danny Alexander has recommended the Royal Navy's fleet of nuclear-armed submarines is cut from four to two.

The Lib Dems said ending the continuous-at-sea deterrent would save £4billion on the estimated £20-£25billion cost of renewal.

However Defence Secretary Philip Hammond warned it would be "reckless" to downgrade Trident, insisting that two subs would not be able to offer the "continuous at-sea deterrence"maintained since the 1960s.

Labour also said that it had seen nothing in the review to change its support for the continuous-at-sea deterrent.

The fleet of four Vanguard-class submarines at Clyde Naval Base which carry the Trident missiles are due to be replaced from 2028, with a decision on whether to replace all four boats coming in 2016

The Liberal Democrats will decide on the party's policy at their conference in Glasgow in September.

Asked whether Trident policy could form a red line in future Coalition negotiations following the 2015 election, Mr Alexander said he hoped the review would influence the thinking of other parties.

He said it would start a debate "which will go on in all political parties, each party will have to think about what position it wants to take ".

The SNP's Westminster leader and defence spokesperson Angus Robertson MP called the review a joke, adding : "The Westminster establishment seem to have forgotten Trident is based in Scotland, and neither the people nor parliament of Scotland want it here."