MILITARY sources have denied as “categorically not true” reports that Britain's entire fleet of attack submarines is currently out of operation due to repair and maintenance work.

Brendan O’Hara, the SNP’s defence spokesman, had described the reports as “chilling” if true and has asked a series of written parliamentary questions about the status of Britain’s nuclear deterrent; he had earlier accused the Ministry of Defence of “terrifying incompetence”.

Initial reports suggested that seven nuclear-powered vessels, including three new Astute class submarines, which cost more than £1 billion each, and four Trafalgar class boats were all currently classed as non-operational.

The UK's Vanguard submarines, which carry Trident nuclear missiles, were said to be in operation but it was suggested this was the first time in decades the Royal Navy had had no attack submarines ready.

However, hours after the reports appeared, an MoD source emerged to insist the claims were false.

"The story is categorically not true,” declared the source. “There are operational, capable and ready attack submarines. Where they might be is clearly sensitive operational information that the MoD will not comment on."

One claim was that defence chiefs had kept the news that all of Britain’s attack submarines were out of use from Prime Minister Theresa May because they “fear her reaction”.

A Royal Navy spokesman said: "We don't comment on specific submarine operations. Britain has a world-class fleet. The Royal Navy continues to meet all of its operational tasking, deploying globally on operations and protecting our national interests as Britain steps up around the world."

Last month, it was revealed that a test firing of a Trident missile by the Royal Navy off the coast of America last June had allegedly failed.

Last week, Sir Michael Fallon, the Defence Secretary, told The Herald: “Secrecy is part of the deterrent. The deterrent's credibility obviously depends on us keeping its operation as secure as possible."

He added: “There are some things that people have to trust the Government on and the nuclear deterrent is one of them. But, let me just reassure you, that we would not have asked Parliament to renew the submarine fleet if we had had any doubts about the safety, capability or effectiveness of the deterrent."

But Mr O’Hara commented: “Reports of all seven attack submarines being out of action are astonishing. If - as reported - our complete lack of any submarine attack capability was ‘kept from the Prime Minister’ - then it is simply indefensible.

“First there was the recent Trident malfunction fiasco, now we have this chilling situation. How can we possibly trust those in charge of our defence when we hear about this utter incompetence and yet another Whitehall nuclear cover-up. It is a scandal.”

The MP for Argyll and Bute said that with the costs of Trident spiralling out of control to the detriment of the country’s conventional defences, then people had a right to know if the deterrent was fulfilling its role. He added that he had now written a series of parliamentary questions to Sir Michael to establish the true status of the UK’s nuclear deterrent.