Workers at the Cowley Mini plant will not be able to return to the production line until at least Monday night.
Union bosses have revealed the entire weekend shift due to start tonight and Monday's early shift will not be working thanks to the fuel strike by Spanish truckers, which has crippled the supply of brake discs to the factory.
And unless the Spanish dispute is resolved, the shutdown could stretch further into next week.
Union convenor Bernard Moss said: "The strike is stopping the tonight's late shift, the weekend shifts and certainly the early shift on Monday morning.
"The situation could change for the worse if other countries become involved."
Bosses say they are unable to estimate how much the enforced shut-down is likely to cost the plant as it has not been resolved, but Mr Moss believes it could run into millions of pounds.
One worker told the Oxford Mail: "They cannot guarantee what work we will have next week. We haven't had any lay-offs like this for a long time."
Plant spokesman Rebecca Baxter said: "We won't really know until it is all over.
"We will have to take a view on Monday."
Ms Baxter confirmed that all workers involved will be paid.
She added: "There are agreements in place to deal with extraordinary situations like this. "We are very grateful to our (employees) for their understanding. We operate a flexible shift pattern and can turn production up in response to demand."
The strike by Spanish hauliers, who are protesting over soaring fuel prices, has blocked roads and hit production and exports out of the country.
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