"We reject the report," Opel spokesman Ulrich Weber said following a pre-released copy of a report in Thursday's Frankfurter Allgemeinen Zeitung based on two unnamed members of the supervisory board.

"We have said several times that there is a reduction of staff but we are not going into concrete figures," Weber said.

Under pressure from US parent General Motors to drive back to profit, Opel announced last month that about half of the 22,100 people who work at its four production plants in Germany would be hit from September by short-time work schemes until the end of the year.