Staff at Faslane (pictured) and Coulport naval bases have begun a series of strikes
Members of the Unite union – who work in roles involving radiation monitoring, weapons support, cleaning, logistics, maintenance and repairs – are taking action over what they claim is a "systematic campaign to undermine workers" by employer Babcock Marine.
Faslane is home to Britain's Trident nuclear deterrent and the Royal Navy's entire submarine fleet is to be based at the site from 2020.
A continuous overtime and on-call ban got under way at midnight on Friday and will affect all areas at the bases, including the Nuclear Operations Department, the union said.
Faslane is home to Britain's Trident nuclear deterrent
Our members have been forced into this action today
Unite regional officer Stephen Deans
Unite members will also begin a series of staggered periods of strike action up to June 15.
The union says Babcock Marine is considering the outsourcing of services to private companies.
Unite regional officer Stephen Deans said: "Our members have been forced into this action today.
The Royal Navy's entire submarine fleet is to be based at Faslane from 2020
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"Management at Babcock Marine have engineered a complete breakdown of normal relations with workers.
"Our fear is that they want to try and undermine workers' rights so they can cut jobs and service quality through more outsourcing."
Defence Secretary visits UK nuclear submarine Fri, January 22, 2016
Defence Secretary Michael Fallon visits HMS Vigilant, one of the UK's four nuclear warhead-carrying submarines at Royal Navy’s Faslane nuclear base on the Clyde.
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Defence Secretary Michael Fallon visits HMS Vigilant at HM Naval Base Clyde, also known as Faslane in Scotland
A continuous overtime and on-call ban got underway at midnight on Friday
The union believes that the action will cause major disruption to the day-to-day services provided by the firm, Mr Deans said.
Babcock has previously voiced its disappointment over the decision to strike.