Defence departments and arms companies can usually explain away embarrassing failures in the development of new military hardware. There is a ready answer: mistakes are an inevitable part of the process of trial and error at the cutting edge of technology.

But the Ministry of Defence cannot fall back on such an excuse in the catastrophic test-firing of the UK’s Trident II D5 ballistic missile in June last year off the coast of Florida. This was not some revolutionary new development still at the experimental stage.

May refuses to confirm whether she knew about Trident 'malfunction' Read more

The missile completed its design stage in 1989 and was deployed a year later. Nor was the Vanguard-class nuclear submarine that fired it, HMS Vengeance, new. It has been in service since 1999. So there should not have been the kind of malfunction that saw the missile targeted in the direction of west Africa head off in the opposite direction towards the US mainland. Any teething troubles should have been worked out long ago.

The problem, according to defence sources, was not the missile itself or the launch system. The missile, they say, did not fail and veer off towards the US. The problem appears to have involved telemetry data, information gathered from various points and fed to the missile. There seem to have been a communication breakdown involving directional data. When this became obvious, the test was aborted.

This explanation is alarming enough and the MoD is braced for a series of questions on Monday from opposition parties.

The case made by proponents of the nuclear weapon is that any attack on the UK will result in inevitable retaliation. The whole basis of the argument is undercut if the UK cannot guarantee that it is capable of hitting the right target or even the right country.

The Scottish National party’s Westminster defence spokesman, Brendan O’Hara, along with his party colleagues, is to put down a series of parliamentary questions and call for an emergency debate. O’Hara said there was a political issue of whether there had been a deliberate cover-up on the part of the prime minister, Theresa May, before a key Commons vote on the renewal of the Trident nuclear programme, but there was also a technical issue.

“There is no suggestion this was a prototype or an experiment,” he said. “A lot of planning and attention had gone into this. There was a loss of control. So it is deeply worrying.”

A former head of the Royal Navy, Adm Lord West, criticised the government for failing to come clean at the time. He told Sky News: “Now they have to reassure us because they were so stupid not to let us see what was going on in June.”

The debate in the run-up to the Commons vote in July last year was dominated by issues such as the cost, the morality of nuclear weapons and whether technological change – such as the use of underwater drones – would make nuclear submarines redundant. Few, if any, questioned the possibility of such a malfunction involving a missile.

Lockheed Martin, which makes the missile, says on its website there have been more than 150 successful test flights since design completion in 1989, a record, the company boasts, “unmatched by any other large ballistic missile or space launch vehicle”.

Most of the tests are carried out by the US navy. The UK, on a tighter budget, conducts fewer such test firings because of the cost: the missiles come in at £17m each. There have been only five such tests this century: in 2000, 2005, 2009, 2012 and last year.

HMS Vengeance had completed a refit and the test was to demonstrate that it was ready to resume active service. Defence sources, playing down the scale of the malfunction, pointed out that Vengeance did resume active service in June last year, the suggestion being that the problem could not have been regarded as that serious.

But opposition parties do not see it that way. They will press for answers tomorrow and beyond. A week on Monday it is Commons defence questions and ministers can brace themselves for a further inquisition into why such a spectacular and disturbing failure could happen.