DONALD TRUMP could have his finger poised over Britain’s nuclear button within 18 months, one MP claimed yesterday amid an ill-tempered Commons clash over Trident renewal.

SNP defence spokesman Brendan O’Hara rubbished claims that Trident is an “independent nuclear deterrent,” saying the US president has the final say over firing the weapons.

Mr O’Hara quoted a 2006 defence select committee report that said: “It is difficult to conceive of any situation in which a prime minister would fire Trident without prior US approval.”

Pointing out that Mr Trump is leading the race to become the Republicans’ US presidential candidate, he asked: “Does anyone seriously think that Trident makes the world a safer place?”

“Possessing Trident isn’t about defence,” he added. “It’s about the illusion of continuing past glories regardless of cost.

“To put it in a more colloquial way, we’re acting as having a fur coat and nae knickers.”

Tory Defence Secretary Michael Fallon delivered his own dire warnings over security as he defended Trident spending.

“Our allies and our adversaries will be paying attention [to the vote],” he told MPs. “This is not a time to gamble with our security.”

On jobs, he added: “Workers on the Clyde don’t want parliamentary motions. They want to be sure of a pay cheque every month. They want to make sure they have a job.”

Mr O’Hara, whose Argyll & Bute constituency includes the Faslane naval base where the Trident subs are stationed, said it could have a “bright non-nuclear future.”

A fractious — and at times farcical — debate came a day after the government published its defence review, which revealed that the cost of four new submarines had increased by £6 billion.

Shadow defence minister Toby Perkins said the SNP was more interested in scoring “cheap political points” against Labour than scrutinising the government decision.

With Labour MPs told to abstain on the vote, which Labour branded a “political stunt,” the SNP’s motion was defeated by 330 to 64.

Veteran Kelvin Hopkins was among a handful of Labour MPs to vote with the SNP, Plaid Cymru and Green MP Caroline Lucas against Trident renewal.

Former Labour shadow defence secretary Des Browne weighed in to the party debate over Trident yesterday saying the submarines could soon be “rendered obsolete.”