LONDON (Reuters) - Ford (>> Ford Motor Company) will announce on Thursday that it is closing its van factory at Southampton, ending more than a century of vehicle production by the company in Britain, trade unionists and a source close to the U.S. car maker said.

The move, which could see some 530 British jobs cut and leave Ford producing only engines and other parts at its remaining plants in the country, is designed to stem losses in Europe by slashing fixed costs at underused manufacturing sites.

It comes a day after Ford said it would shut its 48-year-old Genk plant in Belgium by 2014, with the loss of 4,300 jobs, as part of a wide-ranging restructuring program.

The firm has summoned senior officials from its employees' trade unions to an emergency meeting at 10 a.m. (5 a.m. EDT) at its national headquarters in Basildon, near London.

One of the sources said that Ford will also unveil plans to produce new diesel engines at its nearby Dagenham plant, which employs some 4,000 staff making diesel engines and panels.

The Swaythling factory at Southampton, on England's south coast, has built about 6 million Ford Transit vans in 45 years but would cease production at the end of 2013, said one source, who expects the company to move Transit production to Turkey.

"Ford will move Transit production to Turkey where the wages for staff are so low Britain just can't compete," said Roger Maddison, the Unite union's national officer for the automotive industry. "The Transit van is associated with the ?white van man' tradesmen in Britain and is iconic, like London's black cabs, and it will be sad to see it go."

Earlier this week Manganese Bronze (>> Manganese Bronze Holdings plc), maker of London's black taxis, said it is set to appoint administrators after failing to secure funding needed to survive, putting hundreds of British jobs at risk.

Ford employs 11,400 at British sites which also include Halewood, near Liverpool, and Bridgend in South Wales.

Securing increased production by foreign-owned car makers based in Britain has hitherto been one of the few bright spots in Britain's drive to boost manufacturing.

Earlier this year, General Motors Co (>> General Motors Company) opted to build the next generation of its Astra compact in Britain, instead of at its German plant in Bochum.

Japan's Nissan (>> Nissan Motor), Toyota (>> Toyota Motor Corp.) and Honda (>> Honda Motor) as well as Tata Motors' (>> Tata Motors Limited) Jaguar Land Rover have all committed to production in Britain in recent months.

The shutdown of Ford's Southampton plant would be the fourth European vehicle plant closure announced this year, after PSA Peugeot Citroën (>> PEUGEOT) said it would close a site near Paris and General Motors' decision in May to shutter Bochum.

The past two years have also seen plant closures by Fiat (>> Fiat SpA) in Sicily, General Motors in Belgium and Saab (>> Saab AB) in Sweden.

Ford declined official comment on plans for its British operations.

(Editing by Kate Holton and)

By Rhys Jones