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.