The Unite Union is calling for action to save 240 jobs at Marshall in Cambridge.
Unite are asking the city's MP Julian Huppert to put pressure on his Liberal Democrat colleague, the Business Secretary Vince Cable, to support Marshall.
Up to 240 jobs are under threat at the company's aerospace and defence divisions, and at the company's site in Mildenhall.
Marshall is Cambridge's biggest private employer, but has been hit by a decline in Ministry of Defence contracts.
Unite say the threat of job losses is particularly hard on workers in the run up to Christmas.
– Paul Bouch, Unite regional officer
“Cambridge can’t afford to lose these skilled engineering jobs – the city needs a balanced economy and can’t rely on the two universities, Addenbrooke’s hospital and the companies operating in Silicon Fen. It also needs a strong manufacturing and engineering base.
“Unite will be fighting very hard to retain as many jobs as possible at Marshall in the days and weeks ahead.”