Prime Minister Theresa May has failed to confirm whether she withheld important information from the House of Commons about a "serious malfunction" in the UK's nuclear weapons system days before the issue was debated.
It follows a Sunday Times report which revealed that an Trident II D5 missile experienced an alarming failure after being launched from a British submarine off the coast of Florida in June last year.
The newspaper, citing senior naval sources, said the incident was then covered up by Downing Street because if the information was made public, it would damage the credibility of Britain's nuclear deterrent.
That information was even more sensitive in light of the vote of whether the £40bn ($50bn) Trident programme should be renewed.
However, appearing on BBC's The Andrew Marr Show on Sunday (22 January), the prime minister repeatedly averted questions on the alleged cover-up.
Marr asked May: "When you made that first speech in July in the House of Commons about our Trident nuclear defence, did you know that misfire had occurred?"
"Well, I have absolute faith in our Trident missiles," replied May. "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 and an independent nuclear deterrent in the future."
With a look on his face that signified he was not getting a straight answer, Marr interrupted: "Did you know that it happened?"
May said: "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. Jeremy Corbyn thinks we shouldn't defend our country–"
"But this is a very serious incident. Did you know about it when you told the House of Commons?" Marr interrupted.
The prime minister said: "The issue we were talking about in the House of Commons was a very serious issue: it was about whether or not we should renew Trident, whether we should look to the future and have a replacement Trident.
"That's what we were talking about in the House of Commons, that's what the House of Commons voted on for. I believe in defending our country. Jeremy Corbyn voted against it. He doesn't want to defend our country with an independent nuclear deterrent."
Not satisfied with the response, Marr said: "Prime minister, did you know?"
After a long pause, May said: "There are tests that take place all the time [there have only been five tests this century] for our nuclear deterrents. What we were talking about in that–"
"OK, I'm not going to get an answer to this," Marr interrupted once again.
Defence Secretary Michael Fallon is expected to be called to the House of Commons to explain the test failure, with Labour MP Kevan Jones calling for an inquiry into the incident.
"The UK's independent nuclear deterrent is a vital cornerstone for the nation's defence," he said.
"If there are problems, they should not have been covered up in this ham-fisted way. Ministers should come clean if there are problems and there should be an urgent inquiry into what happened."