A Trident II, or D-5 missile, is launched from an Ohio-class submarine

Trident suffered navigation problems 'years' before one of its missiles malfunctioned and veered off course in a test that was covered up by Number 10, it has emerged.

United States defence department documents show more than £1.4billion has been spent repairing faults and modernising the guidance system in the missiles in the last six years.

And a source has revealed a cover-up of a test in 2011 where a Trident missile fired by the US Navy may have failed.

Last week it was a revealed a news blackout had been enforced when a missile test had failed in June last year, just as MPs were going to vote on renewing Britain's deterrent.

According to the Sunday Times, the Trident II D5 has had consistent problems with its gyro guidance system apparently caused by a chemical reaction within its ageing components.

An extra £215million was diverted to fund the unexpected work.

A senior naval source told the Sunday paper the British test had failed when the missile veered off course, possibly toward the American mainland.

Theresa May was repeatedly asked on Andrew Marr's show whether she knew about the failure when she spoke to the Commons about renewing Trident

In a statement on Saturday, the MoD said: 'We have absolute confidence in our independent nuclear deterrent.'

Michael Clarke, former director-general of the Royal United Services Institute told the Sunday Times the documents were a clear indication that the US navy is determined to drive down production costs of the missiles.

On January 23, US officials confirmed an 'anomaly' did lead to the failure of a British Trident missile test despite the refusal of the Defence Secretary to give MPs details.

Sir Michael Fallon branded reports of the missile failure 'speculation' and insisted HMS Vengeance was successfully recertified and back on operational duty.

A US defence official with 'direct knowledge' of the incident said the anomaly triggered self destruct procedures that involved crashing the Trident missile into the sea off Florida, CNN said.

Prime Minister Theresa May refused four times in an interview to say if she was aware of the major malfunction before she led July's Trident debate.

US defence documents show there were problems in 2011 that were also covered up

The Trident II D5 missile is believed to have veered off course during a test near the coast of Florida last June.

But Mrs May did not mention the failed test when the Commons voted in July to spend £31billion on four new Trident submarines.

The former head of the Royal Navy blasted No10 over its 'bizarre and stupid' decision to 'cover up' a major malfunction in the UK's Trident nuclear missile deterrent and said it made Britain look like North Korea.

Admiral Lord West, who led the Navy from 2002-2006 and later served as a security minister, said the decision not to admit the failed test was 'extraordinary'.

He said the cover-up was probably the work of some 'silly' special adviser [Spad] trying to be 'clever'.

'The whole point of testing and firing things is to see that they work. What I am shocked by is why the Government didn't come clean about it,' he told the BBC.

'If a firing goes wrong, you should say that it's gone wrong unless you think there's something that means so fundamentally wrong that the whole system is no longer viable.

'And from what the Government says that there was a minor glitch with the missile and they're quite happy with the system still, in which case go ahead and let people know.'

Mrs May was repeatedly pressed on her knowledge of the failed test on the Andrew Marr Show.

But she dodged the questions, saying: 'When I made that speech in the House of Commons, what we were talking about was whether or not we should renew our Trident, whether or not we should have Trident missiles, an independent nuclear deterrent in the future.

'I think we should defend our country, I think we should play our role in Nato with an independent nuclear deterrent.'



