FG Wilson cutting up to 260 jobs
Up to 260 jobs are to go at FG Wilson by the end of the year.
The Larne-based engineering firm said it was restructuring its small generator set business to improve efficiency and competitiveness.
It said it was also moving production of one of its generators to China, affecting about 160 agency workers.
The company, which makes diesel and gas generators, said they wanted "to build the product closer to its growing customer base".
"Resources are in place to assist the workforce through this transition," the company said in a statement.
DUP assembly member Alastair Ross said it was "a terrible blow for workers, and evidence that local companies are not immune from uncertain global market conditions".
Workers at the firm have been hit by a series of lay-offs in recent years as the global downturn reduced demand for generators.
FG Wilson was established by the late Fred Wilson and has been owned by US-based Caterpillar since 1999. Mr Wilson died, age 84, in 2010.
The firm is one of Northern Ireland's biggest exporters - 92% of its turnover in 2010 related to exports.