A safety breach at the Faslane nuclear base caused 20 workers to be exposed to radiation whilst repairing a leaking tank on a Trident nuclear weapons submarine. Newly released documents obtained using a Freedom Of Information (FOI) request by the campaign group the Nuclear Information Service revealed a number of safety incidents.

According to the report, the workers were exposed to a low dose of ionising radiation at the same time a nearby reactor was undergoing trials. The Ministry of Defence (MoD) has said that no one was harmed in the incident, which took place in August 2012.

The report said: "There was a prolonged and repeated failure of the SS [ship's staff] to understand and control the radiological hazard they were creating." It also identified "poor communication" and "a lack of understanding of the magnitude of the hazards present when operating a reactor" as contributing factors.

The Nuclear Information Service is a not-for-profit organisation that promotes public awareness on the risks and costs of the UK's military nuclear programme. The reports they obtained also revealed that in April 2012 a training team was allowed to enter a radiation exclusion zone without being issued with dosimeters, devices that measure exposure to ionising radiation.

In two other incidents a sailor working on a submarine at the base left it with a sponge bung without checking for contamination. And in December 2013 an employee exposed himself to radiation after removing some grills from an external tank and put his head inside.

SNP defence spokesperson Brendan O'Hara MP said: "The MoD - once again - stands accused of a very poor approach to radiation safety at the Faslane base. When it comes to protecting our armed forces personnel, the contractors working at the base, as well as the wider community, nuclear safety must be paramount.

''These incidents and how they were subsequently handled, pose real and serious questions , not just about nuclear safety procedures at the base - but also whether the regulator the ONR is doing enough - and quickly enough - to address these concerns. The MoD must investigate and explain why these failings occur and lay out precisely what it is doing to get it sorted.''

A MoD spokesman said: "Safety at Clyde naval base is of paramount importance and none of the events in this report caused harm to any member of staff or the public. Investigations were carried out and measures put in place to prevent such incidents from occurring again, and we continue to conduct rigorous monitoring as part of our commitment to maintain the highest standards."