Prime Minister Theresa May was told about a military exercise in which a Trident nuclear missile failed a key test, Downing Street has confirmed.

No 10 said that "on taking office the Prime Minister was briefed on a range of nuclear issues including this".

During a television interview on Sunday, Mrs May refused to say four times if she had been told about the test result before MPs voted to replace the nuclear deterrent.

The Conservative leader evaded four direct questions about the launch of an Trident II D5 missile from a British submarine off the coast of Florida in June.

The cause of the failure remains top secret but the Sunday Times reported that the missile – which was not armed – may have veered off in the wrong direction towards America.

No 10 also said that the Conservative government had “absolute confidence" in the nuclear system, which is based on the Clyde.

First Minister Nicola Sturgeon has called for “full disclosure” over the incident while Labour leader Jeremy Corbyn described the test as a “pretty catastrophic error”.

The former head of the navy, now a Labour peer, Lord West said it was “bizarre and stupid” of ministers not to come clean.

Over the weekend a UK Government spokesman said: “In June the Royal Navy conducted a routine unarmed Trident missile test launch from HMS Vengeance, as part of an operation which is designed to certify the submarine and its crew.

“Vengeance and her crew were successfully tested and certified, allowing Vengeance to return into service.”