Babcock axes 500 at Devonport dockyard
About 500 workers at Devonport dockyard are to lose their jobs in a round of cuts by Babcock International.
The company, which services Royal Navy warships and submarines, said it was "a necessary step in sustaining the company's future".
"We recognise that this is a worrying time for those colleagues who are affected," it said, adding it would work with unions.
The yard is the sole nuclear repair and refuelling facility for the Royal Navy.
Luke Pollard, Labour MP for Plymouth Sutton and Devonport, tweeted: "Very concerned to hear of job losses at Devonport."
He told the BBC that the firm had warned of job cuts last year, but 500 was more than he was expecting.
And he said that "clarity" was needed from the firm on what jobs were going.
"It looks like being another very bad day for Devonport," he said.
"The yard is so important for our industry because it supports thousands of jobs in the wider economy."
The firm, which employs about 5,000 people at the yard, said the cuts followed a 12-month "review of our operations to ensure that as a business we remain competitive".
Plymouth Moor View Conservative MP Johnny Mercer tweeted that the move was "deeply disappointing".
The Devonport base has been the home of Royal Navy flagship HMS Ocean, which came home for the final time in February before being sold to Brazil.
It is also home to a number of frigates and Trafalgar-class submarines as well as 13 laid-up nuclear submarines which are awaiting dismantling.