Lib Dems back Trident replacement

The Liberal Democrats have signalled their support for replacing Britain's nuclear weapons system – but said the number of missiles it includes should be halved.

Party leader Menzies Campbell said a nuclear-free world was "highly desirable" but admitted that with the threat of North Korea and Iran obtaining nuclear weapons, "it would be unwise" for Britain to abandon its own.

As a compromise, the Lib Dems have published proposals for the number of missiles to be cut by half to 100, carried on three submarines. To allow time for this issue to be discussed properly, they call for the lifespan of the current system, Trident, to be extended.

The announcement comes ahead of the publication of the government white paper on Trident on Monday. Ministers have been reviewing the options for the past few months and are expected to put forward a case for replacing the weapons system.

Labour is divided over the issue, and a number of left-wing backbenchers have already come forward in opposition to replacing Trident, saying it would breach the UK's obligations under the nuclear non-proliferation treaty.

The government denies this, saying the treaty requires them only to continue to reduce the number of nuclear warheads it possesses. Both Tony Blair and Gordon Brown have expressed their support for keeping some kind of independent nuclear deterrent.

Speaking this morning, Sir Menzies said reducing Britain's missiles and extending the life of Trident to 2014 would "be sufficient to provide for Britain's ultimate security until we have more certainty about proliferation".

He said there was no need to take the decision now, despite the prime minister's belief otherwise, and the announcement that MPs would vote on the issue in February following a three-month consultation on the white paper plans.

"A nuclear weapon-free world is highly desirable. Cutting our stockpile in half would send a strong signal that nuclear disarmament is back on the international agenda and that Britain is prepared to act first," Sir Menzies said.

"Britain could at anytime choose to scrap its nuclear deterrent completely if the strategic situation were to be favourable, and this option remains on the table."

Today's proposals will be put to the Lib Dem federal policy committee and then voted on by delegates at the party's spring conference in Harrogate.