Theresa May is facing growing demand to reveal what she knew about a failed Trident missile test.
The Prime Minister refused to confirm or deny knowledge of the test four times over the weekend after the Sunday Times revealed the malfunction.
A Trident II D5 missile, fired from a submarine off the coast of Florida, had headed towards the US instead of Africa last June.
Just weeks after the test, MPs approved the £40 billion Trident renewal programme - something which has fuelled the latest criticism.
Now May is being urged to offer MPs honest answers in Parliament about what she actually knew of the glitch.
Since the Sunday Times' article, Number 10 has been criticised for remaining coy on the subject.
Business Secretary Greg Clark said it was the long-standing policy of the Government not to comment on the tests of weapons systems.
But asked if knowledge of the failed test could have influenced the MPs' decision, shadow defence secretary Nia Griffith: "We don't know because we don't know exactly what happened, so we can't speculate on that until we have a full report, and that's what we're calling for today."
She told BBC Breakfast: "The incident itself speaks for itself, if the reports are true, that a missile veering off course is something to be extremely concerned about.
"But we need to have the full detail of exactly what did happen and why this occurred."
Griffith said the issue was so important that May "certainly should" have answered questions on it.
She said: "It's such a serious incident she is bound to have known and what she needs to tell us is did she know before she gave a major speech on Trident just days after she became prime minister.
"It's not the sort of thing you would forget if you had been briefed about it in the preparation for that speech."
Chairman of the Commons Defence Committee, MP Julian Lewis, said that while the decision to apparently cover up the problem was taken under David Cameron, the Government would at some point have to explain what happened.
"This sort of event is not one you can play both ways. These tests are routine but infrequent in this country," he told BBC Radio 4's Today programme.
"Whenever they work, which is 99% of the time, film is released of them working so whichever person decided they wanted to draw a veil over one that didn't work should have been sacked."