Theresa May, on Sunday's The Marr Show, refused to say whether she knew that a Trident missile reportedly misfired in June.
The prime minister declined four times to answer the questions about the launch of an unarmed Trident II D5 missile from a British submarine off the coast of Florida, which veered off its original course.
Admiral Lord West, the former head of the navy, has said it was "bizzarre and stupid" that ministers kept the reported malfunction quiet.
He told Radio 4's The World This Weekend:
If a firing goes wrong you should say that it’s gone wrong unless you think there’s something that means it’s so fundamentally wrong the whole system is no longer viable.
From what the Government say there was a minor glitch with the missile and they are quite happy with the system still - in which case go ahead and let people know.
Otherwise we are a bit rather like the Soviet Union used to be, or like North Korea or China, where they won’t admit to things going wrong.
Lord West demanded the Government come to parliament to explain the "absolutely stupid" decision to keep quiet, and reassure MPs and the public that the system is operating properly.