Moving the nuclear deterrent out of Scotland would be the single biggest issue of independence, costing a “gargantuan” amount of money and taking a very long time, said Nick Harvey, the armed services minister.
However, he said the Ministry of Defence had not made contingency plans for the possibility because it did not believe that the people of Scotland would vote to leave the union, in the government’s first detailed remarks on the subject since the Scottish referendum was announced.
The Scottish National party has said it will hold the vote in 2014 and has made clear since 2009 there would be no room for nuclear weapons in an independent Scotland.
Rehousing the submarines that carry the nuclear ballistic missiles that provide the UK’s deterrent, would be “fraught with difficulty, a very, very challenging project, which would take a very long time to complete and cost a gargantuan amount”, Mr Harvey told the Commons Scottish affairs committee on Wednesday.
The cost would “dwarf” the £3.5bn spent on upgrading the facilities for the deterrent in Scotland.
The MoD only last month managed to balance its budget, saying it had eradicated the £38bn black hole left by decades of overspending.
A continuous at-sea nuclear deterrent is the cornerstone of defence policy and a priority for the Conservative-led coalition government. The Conservatives want to maintain the deterrent by replacing the ageing submarine-based system that launches the Trident D5 ballistic missile. Liberal Democrats are seeking a cheaper alternative.
Britain will have to take a final decision before 2016 on whether to spend £20bn building four submarines to carry the deterrent, located at the Scottish bases of Faslane and Coulport. But those weapons could be without a permanent home as early as 2014, the expected date of the referendum.
The standard of safety required to move the nuclear arms would be “enormous”, Peter Luff, minister for defence procurement, told the committee. He said building a base would take much longer than conventional projects, noting constructing just one jetty had been “a huge struggle”.
But William Walker, professor of International Relations at the University of St Andrews, said: “The disarmament of Scotland would be tantamount to disarmament of the United Kingdom if Trident could not be relocated.”
Military experts estimate it would take 20 years to rebuild a base for the nuclear weapons.
Mark Lynch, an analyst at the Royal United Services Institute think-tank, goes as far as to say the UK must be prepared to threaten to veto Scotland’s entry into the EU to keep the nuclear deterrent in Faslane.