The Ministry of Defence is being urged to reveal details of a nuclear incident that took place at Faslane naval base earlier this year.

Figures show that a Category A event occurred at HMNB Clyde between 1 January and 22 April.

The Ministry of Defence (MoD) defines Category A as the most serious – however, it has claimed the incident was categorised as of “low safety significance” and did not pose a risk to the public or result in any radiological impact to the environment.

HMNB Clyde is based on the banks of Gare Loch at Faslane in Argyll and Bute.

It is the Royal Navy’s headquarters in Scotland and is home to Britain’s nuclear submarines, which includes the Vanguard vessels armed with Trident missiles.

Nuclear Site Event Reports (NSERs) detail incidents at nuclear facilities and are classified based on their safety significance and impact.

Responding to a written question earlier this year by SNP MP Dave Doogan, Maria Eagle, minister for defence procurement and industry, confirmed dozens of incidents at Faslane and nearby RNAD Coulport – the storage and loading facility for the Trident programme.

Nuclear site events (22 April 2024 to 22 April 2025):

• Coulport: 13 Category C and 34 Category D
• Faslane: 1 Category A, 5 Category B, 29 Category C, and 71 Category D

Ms Eagle said she could not provide specific details of the Category A or B incidents “as disclosure would, or would be likely to, prejudice the capability, effectiveness or security of any relevant forces”.

She assured Mr Doogan that “none of the events caused harm to the health of any member of staff or to any member of the public and none have resulted in any radiological impact to the environment”.

In a letter to Mr Doogan, UK Defence Secretary John Healey said: “I can confirm that all reported events were categorised as of low safety significance.

“In accordance with the International Nuclear and Radiological Event Scale (lNES) significant safety incidents are categorised at the lowest level – level one of seven.

“Incidents that might fall into this category include equipment failures, human error, procedural failings or near misses where no harm [was] caused to the health of any member of naval base staff, any member of the public, or any resultant radiological impact to the environment.”

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In the past week, concerns have been reignited over the environmental and public health impact of the UK’s nuclear weapons programme.

It comes following an investigation by The Guardian and The Ferret, which uncovered radioactive water from RNAD Coulport had leaked into Loch Long due to faulty old pipes back in 2019.

The secrecy battle went on for six years.

The Scottish Environment Protection Agency (SEPA) reported the discharges were “of no regulatory concern”, while the MoD said there had been “no unsafe releases of radioactive material” into the environment.

In response to the “catalogue of failures”, the SNP’s deputy leader is calling for an “urgent explanation” from the UK government as to what actually happened at Faslane.

MSP Keith Brown said: “Nuclear weapons are an ever-present danger and this new information is deeply worrying.

“With repeated reports of serious incidents at Faslane and now confirmed radioactive contamination in Loch Long, it’s clear these weapons are not only poorly maintained but are a direct threat to our environment, our communities, and our safety.

“Worse still, the Labour government is refusing to provide any details about the Category A incident.”

The MoD said it was unable to disclose the details of the incidents reported for “national security reasons”, but stressed all were categorised as of “low safety significance”.

A spokesperson for the MoD said: “We place the upmost importance on handling radioactive substances safely and securely.

“Nuclear Site Event Reports demonstrate our robust safety culture and commitment to learn from experience.

“The incidents posed no risk to the public and did not result in any radiological impact to the environment. It is factually incorrect to suggest otherwise.

“Our government backs our nuclear deterrent as the ultimate guarantor of our national security.”