Defence Secretary Michael Fallon has dismissed an SNP campaign against nuclear weapons convoys on Scotland's roads as "irresponsible" and "scaremongering" as he claimed the Trident deterrent is more vital than ever.

Speaking on board nuclear submarine HMS Vigilant at Faslane naval base on the Clyde, the cabinet minister hit out at claims that the home of Britain's nuclear arsenal lacks democratic legitimacy in Scotland as the vast majority of the country's elected politicians oppose Trident renewal.

He said that Royal Marine commandos were on hand to offer special protection alongside police and that "every precaution" was taken to protect against every possible risk when weapons are transported.

It follows SNP MP Owen Thompson's call for an immediate halt to transportation of nuclear material through the streets.

He said the idea of weapons of mass destruction being taken through his Midlothian constituency from servicing in England was "absolutely chilling."

He said it posed an "unacceptable risk to public safety" after highlighting the findings of campaign group Nukewatch.

It said convoys carrying nuclear weapons were being parked close to schools and Mr Thompson this week secured a second reading for his parliamentary Bill in the Commons which he says will stop the practice north of the Border. It is unlikely to become law due to a lack of parliamentary time.

Mr Fallon said: "It is scaremongering. There's never been a risk to any nuclear convoy in my lifetime. They're properly protected by heavily armed commandos and military police."

He pointed out the people of Scotland had backed remaining part of the UK in the independence referendum, claiming that it was therefore legitimate for nuclear weapons to be based on the Clyde.

This comes despite 57 of 59 of the country's MPs and a majority of MSPs are opposed to renewal.

He launched an attack on Jeremy Corbyn, claiming the Labour leader and others who advocate ditching Britain's nuclear arsenal hold a "very dangerous" view.

"This base is in part of a United Kingdom that voted to remain in the United Kingdom," he said. "There's plenty of solid, mainstream support for the nuclear deterrent inside Scottish Labour, the Trade Unions, the Scottish Conservatives under Ruth Davidson. Scotland voted last year to remain in the UK and within the defence of the UK to keep the deterrent, the Royal Navy, the RAF and the Army."

Mr Fallon's remarks came as the Ministry of Defencelaunched a public relations offensive ahead of an upcoming vote on whether to commission a next generation nuclear weapons system as the Trident submarines near the end of their lifespan.

Press were invited on board HMS Vigilant and given unprecedented behind the scenes access to the inner workings of the UK's nuclear deterrent and its crew.

While under instruction not to enter the realm of politics, crew members on board HMS Vigilant also played down fears over public safety concerns caused by nuclear convoys.

One, responsible for maintenance of on-board missiles, said: "In order for them to be dangerous they have to go through a whole arming process. There are standard routes and they are transported with exceptional levels of security. It's really complex to make a nuclear weapon go bang. They are not set on a hairline trigger. An absolute multitude of things has to happen in a correctly sequenced order. It's not going to fall over on the back of a lorry and generate a nuclear yield."

Mr Fallon refused to put a date on the contentious vote on Trident renewal, which is expected to expose splits within UK Labour and is certain to be vehemently opposed by the SNP.

However, he said he expected the decision to be taken "shortly" as he "wants to get on with building the votes", narrowing the timeframe down to this year. He cited recent action taken by Russia and said Britain faced threats from rogue states such as North Korea, saying Britain must be "morally prepared" to use nuclear weapons if they are to serve as an effective deterrent.

The secretary of state said he had visited Faslane to "emphasise that the nuclear deterrent has never been needed more than it is today. The world is less predictable, more dangerous."

He added: "We've seen the North Korea nuclear test - now is not the time to start thinking about a world in which we wouldn't have this basic insurance policy."

The Ministry of Defence estimates that acquiring four new submarines to carry the Trident deterrent will cost £31 billion over the course of the 20-year procurement programme, with a further £10 billion set aside to meet any additional unexpected cost increases. However, opponents to renewal claim the price will be far higher.

SNP defence spokesman Brendan O'Hara said: "We are completely opposed to nuclear weapons and will vote against the renewal of Trident at every opportunity, whenever it comes.

"We know that Jeremy Corbyn wants to join the SNP in opposing nuclear weapons but once again we can see his leadership being undermined by a party that he cannot control and with his own Scottish leader Kezia Dugdale's well-known support of Trident.

"Keeping the capability to launch cold war nuclear weapons, and therefore the ability to cause catastrophic and unimaginable destruction, is not a suitable solution to the threats we face in the 21st century."