Theresa May is under pressure to admit what she knew about the misfiring of an unarmed Trident missile, three weeks before a parliamentary vote on whether to renew Britain’s flagship nuclear deterrent system.

The backlash gathered momentum after a disastrous TV interview, on the BBC’s Andrew Marr Show, in which the Prime Minister was asked four times whether she was aware of the incident – but refused to confirm or deny.

Reports in The Sunday Times claim that the launch of an unarmed Trident II D5 missile from a British submarine off the coast of Florida in June malfunctioned.

A source told the paper that the missile could have veered off in the wrong direction after being launched and started heading towards America.

Mrs May did not mention this test in a speech to MPs before the Commons vote, in which she urged them to back renewal, leading to allegations the malfunction has been covered up

Jeremy Corbyn responded to Ms May’s evasiveness by describing the alleged incident, which took place in July, as a “pretty catastrophic error”.

“We understand the Prime Minister chose not to inform Parliament, and instead it came out through the media," he told Sky News.

“It’s a pretty catastrophic error when a missile goes in the wrong direction and while it wasn’t armed, goodness knows what the consequences of that could have been.”

The Labour leader repeated his longstanding belief that the country should commit to nuclear disarmament.

Scotland’s First Minister Nicola Sturgeon said: “This is a hugely serious issue. There should be full disclosure of what happened, who knew what when, and why House of Commons wasn’t told.”

MPs urged Defence Secretary Michael Fallon to make a statement to the Commons on the incident on Monday. Nia Griffith, Labour’s Shadow Defence Secretary, said: “This report of a Trident missile veering off course during a test is clearly a very serious matter indeed, and we need to know exactly what happened.

“It is completely unacceptable that today the Prime Minister chose to sidestep questions on the test and would not even tell us when she knew about the incident.

“I am demanding the Prime Minister come to Parliament tomorrow to give a full explanation to MPs.”

Labour peer and former senior Royal Navy officer Admiral Lord West added it was “bizarre and stupid” to not tell anyone about the test.

On The Andrew Marr Show, the Prime Minister refused to answer four separate questions on whether she knew about the incident prior to the parliamentary vote.

She said: “I have absolute faith in our Trident missiles. It was about whether or not we should renew Trident, whether we should look to the future and have a replacement Trident.

“I think we should defend our country, I think we should play our role in NATO with an independent nuclear deterrent. Jeremy Corbyn thinks differently.”

Julian Lewis, who is chair of the House of Commons Defence Select Committee, told Sky News that Theresa May couldn’t be blamed for any sort of cover up over the issue. “These sort of things are observed by very many people,” he said. “It is surprising really that it has taken this long for this story to come out.

“I don’t think one can blame Theresa May, [if there was a cover up] it will have been in place for a month before she became prime minister.”

Mr Lewis added that the Cameron administration had a “bad record of playing politics with the nuclear deterrent.”