Ford's plans to cut production at its Transit factory in Southampton have angered workers, who have downed tools in protest.
Some 90 employees out of a shift of 500 finished work two hours early, but Ford condemned the walkout as "unconstitutional" and a "distraction".
In response to the global downturn, the factory is already working a four-day week and is cutting Transit production from 75,000 to 35,000 a year.
This has worried the 1,100 staff, who fear the factory could close in the long-term with production transferred overseas.
But the company has previously said it would continue making the Transit panel van at Southampton until 2011, with multi-million pound plans for a specialist vehicle to be made at the plant after that.
Responding to the walkout, a Ford spokesman said: "This is taken seriously by Ford as a distraction from the task of continued supply of Transits to customers in a shrunken and tough market.
"Any form of industrial disruption damages (the) Southampton plant's reputation and does nothing to support its case for future investment and sourcing."
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