Deterrent: Trident decision put off for at least six years

David Cameron said the Government would extend the life of the Vanguard class of submarines which carry the UK's nuclear deterrent, so that the decision to start construction of new submarines need not be taken until "about 2016".

The decision was welcomed by anti-nuclear campaigners and eases potential conflict between the Tories and Liberal Democrats over the future of Trident.

Some Tory MPs fear that such a long delay could undermine the effectiveness of Trident, but Mr Cameron insisted the UK would retain its nuclear deterrent.

The Prime Minister has always maintained that the UK should keep the deterrent, and replacing Trident was a Tory manifesto pledge in the last General Election.

Supporters of Trident have argued that the nuclear industry could be hit unless the system was replaced, threatening thousands of job losses.

The Royal Navy operates 58 nuclear-armed submarine-launched ballistic missiles and around 200 nuclear warheads on four Vanguard-class ballistic missile submarines from Clyde Naval Base on Scotland's west coast.