Car manufacturer Peugeot plans to close its Ryton plant in January 2007, six months earlier than anticipated.
The company announced proposals to close the Warwickshire site in April but the plant was expected to stay open for at least a year.
Some 2,300 jobs will be lost in the closure.
Peugeot is holding emergency meetings with unions today to discuss the plans.
Dave Osborne, spokesman for the Transport and General Workers’ Union, said the company had deceived workers.
“Peugeot built hopes up that there would be work well into next year if people wanted it,” he said.
“But they have dashed those hopes and, worse, denied our members the chance to look for work in the knowledge there was a reasonable income coming in.”
The company said in a statement that almost one-quarter of its workforce had asked to leave in the past month.
“Since moving to one shift in August, the company has received an increasing number of requests to leave from employees wishing to start new jobs, and the rate of these requests is accelerating. This situation has prompted the group to review the timing of the end of activity at Ryton,” it said.
Peugeot has set up a £5m support centre to help staff find alternative work, the statement said.