London  - British trade unions said Tuesday they had agreed a deal to secure the future of two Vauxhall plants belonging to troubled US carmaker General Motors (GM).

The Unite union said the car giant's proposed new owners, Canadian-Austrian car parts firm Magna, had agreed to provide security for the 5,500 jobs involved in return for cost savings.

Magna is in the process of buying both Opel and Germany, and Vauxhall in Britain, from General Motors.

"Following extensive and constructive dialogue between Vauxhall Motors, Magna International, Unite and the British government, we are pleased that the parties have secured an agreement that protects the jobs and prospects of the 5,000 Vauxhall employees in the UK," Vauxhall said in a statement.

"Cost saving and efficiency measures will be implemented which include a two-year pay freeze and other measures and past employee sacrifices will be recognized."

The agreement was the result of a "tremendous team effort between leadership of Unite and the management team at Vauxhall," said the statement.

Unite said the agreement removed the uncertainty surrounding the factories in Ellesmere Port, in the northern county of Cheshire, and in Luton, north of London.

Both plants would be given job security and a future through to 2013, providing a good basis for a long-term future beyond that point, said Tony Woodley, the union's joint leader.

He said that up to 600 jobs could be cut through voluntary redundancies, about half the number the unions had originally feared could be lost.

Union officials had earlier expressed fears for the long-term future of the factories after the German government offered massive help to secure jobs at Opel factories.  dpa