"As far as we are concerned, the loss of 9,000 jobs in Europe is unacceptable," Franz told the German daily Frankfurter Rundschau.
He added that the job cuts were "economic nonsense" and that Opel would anyway lose 10,500 jobs by 2013 through voluntary departures and retirements. Franz is also a member of Opel's supervisory board.
GM has said it plans to cut 8,300 jobs out of Opel's total 50,000-strong workforce in Europe but has not detailed where exactly the cuts will fall. Negotiations on the restructuring are set to resume next month.
Opel has had a dramatic year amid upheaval in the global auto industry triggered by a collapse in sales due to the world economic crisis.
The company was initially put on sale by GM and was due to be sold to Canadian auto parts maker Magna International but the sale was later scrapped.