THE UK needs to keep its Trident nuclear deterrent to maintain its “outsized role” on the world stage, the US defence secretary said yesterday. However, SNP MSP Bill Kidd, vice-president of Parliamentarians for Nuclear Non-Proliferation hit back, calling the weapons system "immoral" and "an obscene waste of money".

Ash Carter, the US defence secretary, also said the nuclear-armed submarines based at Faslane were an "important part of the deterrent structure of Nato".

The cost of renewing and maintaining Trident is put at £167bn between 2028 and 2060.

MPs voted in 2007 to continue the at-sea deterrent and are expected to take a “main gate” decision on whether to have three or four subs later this year.

UK Labour, which is looking at Trident in its defence review, is deeply split over the issue.

Jeremy Corbyn and his shadow defence secretary Emily Thornberry, who is leading the review, oppose renewal, while shadow foreign secretary Hilary Benn is in favour.

Many unions, notably the GMB, also back renewal for the sake of jobs.

Shadow home secretary Andy Burnham, a renewal supporter, last week admitted the party's divisions "may be impossible to reconcile".

Carter told the BBC that Trident enables Britain to "continue to play that outsized role on the global stage that it does because of its moral standing and its historical standing".

"It's important that the military power matches that standing and so we're very supportive of it," he said.

"We depend upon the United Kingdom, the United Kingdom depends on us, that's part of the special relationship.

“We build Joint Strike Fighters together, we build Trident missiles together."

SNP MSP Bill Kidd, Vice President of Parliamentarians for Nuclear Non-Proliferation, said: “Trident is an immoral and redundant weapons system, and an obscene waste of money.

"That's why the SNP will continue to lead the opposition to spending billions on renewing these weapons of mass destruction - and fight tooth and nail against Tory plans for renewal.”

SNP ministers are likely to face questions on the subject in Clydebank tomorrow, when the Scottish Cabinet visits the town.