London — Britain’s Defense Secretary Grant Shapps sought to reassure U.K. lawmakers Wednesday that the country’s nuclear deterrent weapons program was functional and ready to be called upon if needed after a second consecutive missile test reportedly failed. A nuclear-capable Trident II missile test launched in the Atlantic off the coast of Florida on Jan. 30 reportedly splashed back down shortly after launching, according to Britain’s The Sun newspaper. 

The missile was launched from one of the Royal Navy’s HMS Vanguard-class submarines — with Shapps on board to observe — but its first stage booster engine failed to ignite, causing it to fall back down and then sink, according to CBS News partner network BBC News. 

While Britain’s Trident missiles are designed to carry nuclear warheads, they are not armed for test launches.

In a statement to parliament, Shapps confirmed an “anomaly” during the missile test, but insisted that it had “reaffirmed the effectiveness of the U.K.’s nuclear deterrent.”

The BBC said it was the second consecutive test of a Trident missile to fail after one of the rockets veered off course in 2016, also off Florida’s Atlantic coast. The test launches don’t happen often, with each missile costing U.K. taxpayers more than $20 million. 

The cause of the 2016 failure has never been disclosed, but at the time, The Sunday Times newspaper reported the missile had suffered an in-flight “malfunction.”

“The U.K.’s nuclear weapons program is not functioning and needs an urgent rethink,” David Cullen, a former activist who’s now the director of the British monitoring group Nuclear Information Service, told CBS News on Wednesday. “This failure has happened with a backdrop of the navy struggling to maintain [Trident submarine] patrols and ballooning costs.” 

Shapps, however, called the Trident system “effective, dependable, and formidable.”  

“The test reaffirmed the effectiveness of the U.K.’s nuclear deterrent, in which the government has absolute confidence,” Shapps said in a written statement delivered to lawmakers in the British Parliament on Wednesday. “On this occasion, an anomaly did occur, but it was event specific and there are no implications for the reliability of the wider Trident missile systems and stockpiles. Nor are there any implications for our ability to fire our nuclear weapons, should the circumstances arise in which we need to do so.” 

The Campaign for Nuclear Disarmament, a U.K.-based group that has long called for an end to Britain’s nuclear weapons program, derided the test as a “colossal waste of money.”

“We have to ask if this is a good use of the Defense Secretary’s time — going to Florida chasing photo opportunities for what ultimately was an expensive failure,” the campaign’s General Secretary Kate Hudson said in a statement.

The U.K.’s nuclear deterrent program consists of four Vanguard-class submarines, each of which can carry up to 16 Trident II D5 ballistic missiles. At least one submarine is always deployed, with its location among Britain’s most closely guarded military secrets. A second sub waits on standby while a third carries out training exercises and the fourth is brought in for maintenance.

The Ministry of Defense says that since the system was deployed in April 1969, there has constantly been at least one British nuclear-armed ballistic missile submarine quietly patrolling the seas. The “deterrent” principle of the Trident system relies on the U.K.’s global adversaries never knowing the exact location of the deployed submarine.