RFA Mounts Bay is one of the fleet's support ships (Picture: MOD).
Hundreds of workers at the Royal Fleet Auxiliary (RFA) have voted to go on strike in a dispute over pay.
Members of the Rail, Maritime and Transport union (RMT) at the RFA, which supports and supplies the Royal Navy, overwhelmingly backed a campaign of industrial action.
The union said a 1.5% pay increase had been imposed, "undermining" the living standards of the workers.
RMT General Secretary Mick Cash said: "It is disgraceful that our Royal Fleet Auxiliary members, staff delivering the supplies life-line to the Royal Navy that is crucial to our national safety and security, have had a derisory pay increase imposed on them which doesn't even keep pace with the cost of living.
"That amounts to a pay cut in real terms and is wholly unacceptable, and that is why we are now moving to a formal industrial action ballot.
"RMT will not stand by while RFA staff are denied basic pay justice. The union will be stepping up the 'Fair Pay for RFA' campaign which will give the public a chance to show their support for this essential group of workers.
"We remain available for genuine and meaningful talks."
Watch: what does the RFA do?
The union's executive will consider the next step in the dispute.
A Ministry of Defence spokesperson said: “The pay award for RFA personnel for 2018/19 was in accordance with Treasury guidance, and we will continue to work with the RMT for a solution.
“While these discussions continue, RFA operations are unaffected and they continue to support the Royal Navy and British interests around the world.”
The RFA is the uniformed civilian branch of the Naval Service, staffed by merchant sailors.
Their job is to provide logistical and operational support across a range of tasks, from humanitarian missions to counter-piracy.