The chief of the defence staff has defended Trident as a necessary “insurance policy” after the SNP said the future of the UK’s nuclear weapons system would be up for negotiation in post-election talks with Labour.
It comes as Defence Secretary Ben Wallace warned that an SNP-Labour government would represent a threat to national security.
The nationalists have long campaigned for the removal of missile submarines carrying nuclear weapons from their home base on the Clyde at Faslane.
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SNP defence spokesman Stewart McDonald said “discussions over Trident will be a priority” in the event of a hung parliament.
The party’s Westminster leader Ian Blackford told Sky’s Ridge on Sunday programme that the UK should not be investing in the replacement of the missile submarine fleet, which will cost up to £200bn over its lifetime.
Asked if Trident was a “red line” for the SNP in talks with Labour, Mr Blackford said the party will "come up with a wish list" of policies it wants to secure.
"We're been pretty consistent down through the decades that we don't wish to see nuclear weapons on our soil,” Mr Blackford said.
He added: "We would simply say that these weapons are not fit for purpose. The simple fact of the matter is I'm not sure that we're taking our responsibilities for conventional defences as seriously as we should be doing.
"And I think to waste up to £200 billion on these weapons of mass destruction that can never be used is a fallacy."
But appearing on the BBC’s Andrew Marr show, General Sir Nick Carter, the Chief of the Defence Staff, defended the UK’s nuclear deterrent.
“The difficulty is you can’t predict the future,” he said. “And of course, a programme like Trident is one that's a 40 to 50 year programme.
“If you choose not to do something like that now, it will be impossible to get back into it, and who can tell what the world will look like in 2035. So it's an insurance policy.”
Speaking to the Sunday Time, the Defence Secretary said he had “deep concerns" about a "Corbyn-Sturgeon arrangement, a Marxistnationalist alliance [that] puts at risk Scotland and the UK's security in a changing and dangerous world".
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Mr Wallace said: "Russian submarines are in the North Atlantic and there is an aggressive Russian posture across Eastern Europe threatening Nato allies.
“Trident is a really important deterrent against them. Corbyn is rolling the dice over Britain's defence and Sturgeon is doing the same with Scotland's security.
“As ever the SNP want to have their cake and eat it; they want the jobs and the base at Faslane but not the submarines."