Twenty workers at the Faslane nuclear submarine base in Scotland were exposed to radiation in breach of safety rules, according to an investigation by the Ministry of Defence (MoD).

A series of radiation blunders on Trident submarines docked at the Clyde naval port has been revealed in heavily redacted MoD documents obtained by the Nuclear Information Service, a campaign group opposed to nuclear weapons.

Safety procedures were flouted by MoD and contractor Babcock at the Scottish site, the documents show. Breaches included a failure to give visitors radiation badges, a contaminated sponge being taken from a submarine, and another worker being irradiated.

The revelations, which MoD took two years to release, have prompted concern from experts and politicians, who are demanding a major overhaul of safety at Faslane. Prospect, the trade union representing Faslane engineers, promised to support workers worried about radiation poisoning.

The union’s negotiations officer, Richard Hardy, said: “Any incident which involves exposure to radiation is of concern and we will work with Babcock as the employer of our members to ensure that any lessons learned are taken forward as a matter of urgency and also to ensure that staffing and knowledge levels within this critical facility are maintained at the appropriate level.”

Faslane is regulated by an internal MoD watchdog, the Defence Nuclear Safety Regulator. It is not licensed by the government’s Office for Nuclear Regulation, which oversees civil nuclear sites. The MoD said safety at the base was paramount and none of the events described in the reports caused harm to the health of any member of staff or to any member of the public.