A UK Government minister has conceded there is "no deal to be done" over Trident and the UK's nuclear deterrent would be expelled from ­Scotland in the event of independence.

Negotiations on the issue are a ­non-starter because the SNP could never contemplate a compromise, according to Scotland Office minister David Mundell.

His comments are the first insight into how talks to break up the UK could progress.

Officially, the Coalition Government insists it will not "pre-negotiate" ahead of September's vote.

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Trident was expected to be one of the biggest issues of contention in any pre-independence discussions and a major bargaining chip for a government of a newly-independent Scotland.

Scottish ministers have vowed to remove nuclear weapons as soon as safely possible in the event of a Yes vote, with a view to a deadline of 2021.

But experts warn relocating the UK's nuclear deterrent from the Clyde would cost tens of billions of pounds, potentially even forcing the UK into unilateral disarmament.

Mr Mundell said the SNP's public pronouncements on nuclear weapons, and the strength of feeling among many of the party's supporters, meant "they [the SNP] could never - if they were successful in their objectives - they could never go back on the Trident thing. There is no deal to be done."

He added: "I used to think personally, probably there would be some arrangement where Trident could stay just if they [the SNP] were given a lot of money. But now I'm absolutely clear it couldn't, because they are so committed."

He also referred to the unnamed UK minister who rocked the No campaign earlier this month by suggesting the UK Government's opposition to a currency union was a bluff - and that allowing Scotland to keep the pound would form part of a Trident trade-off.

It was obvious the anonymous ­politician was not "somebody who is closely involved with the debate", he said, because "it is a misunderstanding of [the thinking] within the nationalist political movement that they could ever even contemplate that."

He added that the minister involved perhaps wanted to "big their part [in potential negotiations] up".

Mr Mundell suggested the SNP's staunch public stance on Trident had boxed the party in on the issue. Not only was the SNP itself committed to getting rid of Trident, he said, but the party had also successfully "sucked in" the radical left, also bitterly opposed to nuclear weapons, to the nationalist movement.

Mr Mundell's comments will likely concern his fellow Conservative MPs, many of whom are determined to keep the UK's nuclear deterrent but will baulk at spending billions of pounds relocating it from Scotland. The ­Ministry of Defence has already warned the costs of moving Trident would be "enormous".

Last year, Professor Malcolm ­Chalmers, from the highly respected defence think tank the Royal United Services Institute, suggested Trident "might prove impossible to move".

"We don't know because that study has never been done," he said.

Lord West, the former First Sea Lord, has gone even further, suggesting that it could trigger unilateral disarmament for the rest of the UK.

Relocation problems include the fact there is no immediate place for the nuclear deterrent to go. While Milford Haven in Wales and Devonport in Plymouth have been suggested, both would lead to safety fears and almost certainly run into local opposition.

Last night a spokesman for First Minister Alex Salmond said an ­independent Scotland would see an end to nuclear weapons being based in Scotland. He added: "That is a crystal clear and unequivocal commitment that we have never wavered on - unlike the UK Government's stance on Sterling, which has crumbled following the 'currency confession' from a Westminster minister that 'of course' a currency union will happen."