WESTMINSTER parties have been accused of running away from a “serious debate” on Trident, as discussions about the nuclear weapons system turn to mud-slinging and point-scoring.

Defence Secretary Michael Fallon yesterday said that Ed Miliband was ready to “stab the UK in the back” after the SNP reiterated their support for nuclear disarmament.

Labour leader Ed Miliband came out fighting in response, saying he would never “negotiate away our national security”, despite a majority of his own candidates backing the SNP stance on the weapons.

Kate Hudson, general secretary of the Campaign for Nuclear Disarmament (CND), said that all this rhetoric is simply helping the politicians avoid a serious debate on the subject.

In Wednesday night’s TV debate, First Minister Nicola Sturgeon confirmed to Scottish Conservative leader Ruth Davidson that Trident was indeed a red line for the SNP, and repeated these sentiments while out campaigning yesterday.

Fallon said that any influence from the SNP in government with their “child-like view of the world” would be disastrous, saying that we must defend ourselves against our “enemies”.

“The SNP’s child-like world view would sacrifice the long-term security of the UK and play into the hands of our enemies. The nuclear deterrent protects all of Britain and the SNP represents a separatist threat that would dangerously weaken our collective defence,” he said.

As a war of words kicked off, Ed Miliband firmly backed Tory policy, saying: “Our position is continuous at-sea deterrence, like the Conservative Party, renewing Trident, like the Conservative Party, multi-lateral disarmament, like the Conservative Party.”

While Labour and Tory leaders joined together to promise a full like-for-like replacement of Trident, costing an estimated £100 billion, the Liberal Democrats presented their pitch for a reduced system, with Faslane only housing two submarines, rather than the current four.

SNP defence spokesman Angus Robertson MP called Trident “unusable and indefensible”.

He said: “The Trident nuclear missile system is unusable and indefensible – and the plans to renew it are ludicrous on both defence and financial grounds. No politician can say with any credibility that they would ever fire nuclear weapons, which would kill civilians massively and indiscriminately, and create environmental catastrophe.

“Trident is utterly irrelevant to the defence and security challenges we face in the 21st century, and therefore the appropriate number of Trident submarines isn’t four or three – it is zero.”

“As a weapons system designed for the Cold War, the case for Trident is non-existent in 2015, and it will be utterly unlamented if we are successful in getting rid of it.”

Hudson backed Robertson’s view, saying that Trident “does nothing to keep us safe”.

She said: “Senior military figures warn that the £100 billion white elephant of Trident replacement does nothing to keep us safe and is resulting in thousands of jobs in the armed forces being slashed.

“How a blind commitment to squandering our overstretched national resources on a Cold War weapon can be touted as being ‘strong on defence’ is beyond me.”

The Scottish Greens also joined the calls to halt Trident renewal, slamming the “Cold War bunker mentality” of the big Westminster parties and calling for the UK to leave Nato.

A spokesman for the party said: “The Cold War bunker mentality of Labour, the Tories and the LibDems is simply appalling. Rather than renewing immoral nuclear weapons we should be investing in job creation and tackling poverty.”

But he added: “While the SNP share our view on Trident, we must disagree with their position on supporting the Nato nuclear alliance.”

Prime Minister David Cameron backed Fallon’s attacks on Miliband, saying that the Tories are the only party “absolutely guaranteeing a full replacement of Trident”.

A recent study by CND of more than 700 parliamentary candidates from across the political spectrum showed that 80 per cent would vote against the replacement of Trident.