According to the Unite union, Rolls-Royce sent an internal memo to its staff to detail its proposals. The plan puts 378 defence jobs at risk at its Ansty plant, near Coventry, Unite said - nearly half of its 800-strong workforce, reports Sky News.
The union blamed defence spending cuts by the Government and said Rolls-Royce was planning to shut the plant in the next few years.
Rolls-Royce said its civil aerospace business in Ansty was not affected by the plan.
Ian Waddell, Unite's national officer for aerospace and shipbuilding, said the blame for the loss of the highly skilled jobs in the key defence sector lies with the Government and its short-sighted determination to ram through massive spending cuts in the defence budget.
Waddell said work from Germany will be transferred to Rolls-Royce's site at Bristol. He further said bosses at Rolls-Royce had acted "fairly" by giving as much notice as possible to the staff of the company's plans.
The 200-acre Rolls-Royce site at Ansty employs about 800 people and handles the refit and repair of both aeroplane and marine engines.