Ford is to close its Transit van factory and another UK site with the loss of up to 1,500 jobs, sources said.
The grim news was given to union officials at a meeting with the company and was described as "devastating" by one official.
The Transit van plant in Southampton will close next summer, with the loss of more than 500 jobs, while a site in Dagenham will shut at the same time.
Union officials said up to 1,500 jobs will be affected by the news, although some new posts will be created at the Dagenham engine plant which will build Ford's new Panther engine.
It is understood that Ford will offer a generous redundancy package and redeployment to workers who want to stay with the company.
Justin Bowden, national officer of the GMB union, said: "This is devastating news for the workers in Southampton and Dagenham and is very bad news for UK manufacturing. Ford's track record in Britain is one of broken promises and factory closures. There will be a feeling of shock and anger, and Ford's commitment on investment will cut little ice."
Ford employs around 11,400 workers in the UK at plants including Dagenham, Halewood on Merseyside and Bridgend in South Wales. Ford on Wednesday unveiled plans to close its factory in Genk, Belgium, with the loss of 4,300 jobs and said more details of its "transformation" plan for Europe will be given later.
Stephen Odell, chairman and chief executive of Ford of Europe, said: "The proposed restructuring of our European manufacturing operations is a fundamental part of our plan to strengthen Ford's business in Europe and to return to profitable growth."
Mr Odell met union officials to give them the news.
Ford will not make an official announcement on its plans until later. The news emerged two hours after official figures showed that the UK's recession had ended.