A leaked document has revealed that Magna wants to cut a fifth of Vauxhall's workforce if it is successful in taking over the company.
The Times newspaper has revealed the contents of proposal documents shown to the German Government and the head of General Motors Europe on 17 July.
In the documents, Magna International said that it plans to sack 830 workers at the Vauxhall plant in Ellesmere Port, and another 354 at Luton.
However, it is not known whether the documents are final proposals, and they could have been modified following last-minute discussions.
Unions expect that Magna and its main rival bidder, RHJ International, the Belgian industrials group, will sack about 10,000 workers across GM Europe as a whole. However, it has not been made public which workers would lose their jobs.
According to the documents, Magna also reckons that it can return GM Europe to profitability by 2011 and that workers will share 10 per cent of profits.