Vauxhall has cut one third of its Ellesmere Port factory's workforce.
Around 900 workers are to be laid off from the 3,250-strong workforce. The total is slightly lower than expected and the firm hopes the cuts will be achieved through voluntary redundancies.
The Cheshire factory, which makes the Astra and is GM's only factory in the UK, will switch from three shifts to two.
GM is cutting 30,000 jobs in the US and the Vauxhall news follows the closures by TVR, Peugeot and Jaguar in recent months. As with Peugeot's Ryton factory, Ellesmere Port is GM's most expensive European plant.
The decision over where to produce the next Astra, to be taken next year, will be crucial. GM has four plants in Europe - Germany, Poland, Sweden, Belgium and Ellesmere Port - and needs only four production sites for the new car, which due in 2009.
Continental announced on Monday that 240 workers at its Welsh brake factory would be made redundant as it switches production to eastern Europe.