British lawmakers are seeking reassurances about the nation’s nuclear deterrent after reports that a test of the system failed dramatically last month when an unarmed missile crashed into the sea near the submarine from which it was launched.

The Sun newspaper reported on Tuesday that the incident occurred last month while Defense Secretary Grant Shapps was on board the HMS Vanguard to witness the test firing of a Trident missile designed to carry nuclear warheads.

The Ministry of Defense confirmed that an “anomaly” occurred but said “the test reaffirmed the effectiveness of the U.K.’s nuclear deterrent.”

“As a matter of national security, we cannot provide further information on this, however, we are confident that the anomaly was event specific, and therefore there are no implications for the reliability of the wider Trident missile systems and stockpile,” the ministry said.

“The U.K.’s nuclear deterrent remains safe, secure and effective,” it added.

John Healey, the opposition Labour Party’s spokesman on defense issues, said reports of the test failure were “concerning.”

“The defense secretary will want to reassure Parliament that this test has no impact on the effectiveness of the U.K.’s deterrent operations,” he said.

(AP)