The coalition split over the future of Britain's nuclear deterrent has been reopened by a new £1 billion Ministry of Defence (MoD) commitment to powering the UK's nuclear submarines.
Funding set to be announced today is being directed to the Rolls Royce plant in Derby, where nuclear core reactors are built for the Royal Navy's Vanguard and Astute class submarines.
The move by Conservative defence secretary Philip Hammond appears to clash with the coalition's stated position of putting off the final decision on whether to go ahead with renewing Trident until 2016 - after the next general election.
"We're placing orders now for the long lead items that will be necessary to deliver a successor to the Vanguard class submarines in the late 2020s," Mr Hammond told BBC1's Sunday Politics programme yesterday.
"But the actual decision to go ahead and build them won't have to be taken until 2016 and what we're doing at the moment is ordering the things that have to be ordered now to give us that option."
Liberal Democrats are opposed to renewing Trident on a like-for-like basis and are now exploring alternatives to the so-called 'Moscow criterion', which states that a nuclear capability must be able to destroy a country's government and military command to be effective.
That approach is anachronistic now the Cold War is over, Lib Dems are arguing. Former party leader Sir Menzies Campbell argued in a piece for the Financial Times website that Britain could maintain a credible deterrent with a smaller-scale capability.He pointed out that Britain had dropped its nuclear depth charges, nuclear artillery and free-fall bombs in the last 25 years.
"The lesson to be drawn is that when the political context provides safe opportunities to reduce the salience of nuclear weapons we should take them, if necessary by 'independent' decisions," Sir Menzies wrote.
The government also faces pressure on the nuclear issue from north of the border, where Scottish government strategy secretary Bruce Crawford has been speaking out against the submarines.
"What is quite clear from Scotland is that the people of Scotland are opposed to the new nuclear weapons system on the Clyde," he said yesterday.
"I think it's an obscenity that we're going to be pressing ahead at this time with this particular system."