Defence giant BAE Systems is to axe 1,775 jobs across its naval ships business and end shipbuilding at one the country's most historic yards.
The firm said 940 jobs will be lost in Portsmouth, on the south coast, and a further 835 in Glasgow, Rosyth and Filton, near Bristol
Shipbuilding operations will end in Portsmouth in the second half of next year, but an engineering team will be retained to support the new Type 26 warships, which will be built in Glasgow.
BAE said it remained committed to continued investment in Portsmouth as the centre of its maritime services and high-end naval equipment and combat systems businesses.
BAE said it was being hit by a "significant" reduction in workload following the peak of activity on the current aircraft carrier programme.
The grim news was given to workers at a series of meetings at 11am across the affected sites, before they were allowed to go home for the rest of the day.
David Hulse, GMB national officer and chair of the Confederation of Shipbuilding and Engineering Unions' (CSEU) shipbuilding national committee, said: "Following today's announcement from BAE Systems, we are able to confirm that no shipyard will be closing even though there are substantial job losses in the pipeline.
"There is no doubt that this is a devastating day for the UK shipbuilding industry and the company will have justify to us the job losses planned.
"We have arranged a two-day meeting with the company at Farnborough next Monday and Tuesday that will be attended by officers and shop stewards from all the yards and all the unions. This meeting will examine in detail the business case and all aspects for scheduling work in the yards to complete building the carriers, starting work on the Type 26 ships and any other work."
Hugh Scullion, general secretary of the CSEU, said: "The CSEU has been assured that further discussions will take place in the coming weeks with BAE over the future of its marine division, which has huge strategic importance for the UK's defence industry. Getting an agreement which avoids the need for compulsory redundancies will be central to our discussions with the company. The CSEU will also make it a priority to protect the future of the UK shipbuilding industry by securing investment to ensure the industry doesn't just survive but prospers in the future. "
BAE wound down its North East operations earlier this year, with the loss of around 300 jobs.
The defence manufacturer's regional presence now consists of a small specialist engineering team in Newburn.