The Essen-based newspaper said sources at the Bochum-based car maker have told it losses are much higher than previously thought.
The report ramps up the pressure on negotiators trying to find a buyer, as a bridging loan of €1.5 billion will only last until the middle of September with money haemorrhaging out of the company so fast.
A meeting of Opel workers representatives heard on Wednesday that further credit would not be made available, neither from the federal government or the North Rhine-Westphalia state government.
Talks between Opel's US owner General Motors and possible investors, including Canadian giant Magna backed by Russia's Sberbank, are continuing, while Chinese car make BAIC is examining the books.
Fred Irwin, chairman of the advisory board of the Opel trust caused confusion earlier this week when he said that a memorandum of understanding was not legally binding and that GM would talk with anyone who was interested.