The UK Ministry of Defence has confirmed that a Category A nuclear incident – the most severe classification for such events – occurred earlier this year at HMNB Clyde in Faslane, Scotland, home to the Royal Navy’s Trident-armed Vanguard-class submarines.

The incident, which took place between January and April, involved a situation with an “actual or high potential for radioactive release to the environment.” Officials have not disclosed whether radioactive material was released, prompting criticism over transparency.

The admission came in a parliamentary response from procurement minister Maria Eagle, who also revealed multiple lower-level incidents at both Faslane and the nearby Coulport base, where nuclear missiles and warheads are stored. The disclosure follows reports of repeated radioactive water leaks into Loch Long, allegedly caused by ageing infrastructure and inadequate maintenance.

Scottish political leaders have accused the UK government of withholding crucial details, warning that poor upkeep of Britain’s nuclear arsenal poses a direct risk to public safety and the environment.