General Motors will report a 2011 loss of "slightly more than US$1bn" for its European Opel/Vauxhall division on Thursday, monthly Manager Magazin reported in its online edition citing "insiders."

Opel sold slightly more than 1m cars last year, according to the report, less than previously planned.

According to Dow Jones, Manager Magazin said the closure of Opel's Belgian plant in Antwerp cut around $100m from earnings last year and the insolvency of GM's former Swedish brand Saab another "high double-digit million sum".

An Opel spokesman said the reported sales volume was wrong because Opel and its UK sister brand Vauxhall sold over 1.2m vehicles in Europe last year.

But he declined to comment on the earnings figures ahead of the official release on Thursday.

Bloomberg News, in a pre-results report on GM, said the darkest cloud on the automaker’s horizon is Opel, the biggest contributor to the $14.7bn in European operating losses since 1999.

“What investors are afraid of is that the more Opel is in the news under a negative light, it only makes the restructuring more difficult; it potentially even harms the brand to some extent in terms of market share and sales,” Itay Michaeli, a New York-based analyst at Citigroup, told Bloomberg.

“Patience is slowly wearing thin to at least achieve a credible plan to get back to break even.”

While North American operations may have delivered $1.1bn in earnings before interest and taxes, the average of three analysts’ estimates, losses in Europe probably rose from the third quarter to $358m, undermining the company’s progress, the news agency said.

GM said in November that it couldn’t break even in Europe, and chairman Dan Akerson has since dispatched several top lieutenants to Opel, including vice chairman Steve Girsky, who took over as chairman of the Ruesselsheim, Germany-based unit. The drama is weighing down GM shares, Michaeli said.

GM Europe lost $292m in the third quarter and $582m in the first nine months of 2011. In 2010, it lost $568m in the fourth quarter and $1.76bn for the year, including restructuring charges. The analysts’ estimates for the final three months last year don’t include any one-time items. Since 1999, the unit has lost $14.7 billion, Bloomberg added.

While GM shares have risen 25% so far this year, they remain 24% below the $33 level of the automaker’s 2010 initial public offering. With a market capitalisation of $39.6 billion, GM is trading at 6.24 times earnings, less than half the 14 times earnings that investors pay for the S&P 500 Index.

“Whenever you have a company that’s got a major division losing money without any tangible end in sight to those losses, it does tend to depress the overall multiple,” Michaeli told Bloomberg News.

The news agency noted that, while Opel CEO Karl-Friedrich Stracke has told employees that the automaker hasn’t made any decisions on shutting factories, reducing headcount or shifting production, he said “there are issues that need to be addressed.”

GM is looking to find greater cost savings between Opel and Chevrolet operations in Europe, Tim Lee, president of GM’s international operations, said last month. Lee was appointed to Opel’s supervisory board last year. GM may move some work from Korea to Europe to boost revenue and use assets there, three people familiar with the matter have said, according to Bloomberg.

GM, which has already trimmed its European workforce by 5,800, may look to close plants in Ellesmere Port, England, and Bochum, Germany, Brian Johnson, an industry analyst at Barclays Capital, told Bloomberg. GM’s plant utilisation rate in Europe is 78% and is expected to fall to 69% this year and more after that, Johnson said.

Over the next 12 to 18 months, Adam Jonas, an analyst at Morgan Stanley, said he expects GM to push cutting 3,000 to 5,000 jobs.

“The conditions are ripe for capacity to exit, not just at GM but also Renault, Peugeot and Nissan,” Jonas told Bloomberg. “We’re a bit sceptical. We’re not entirely convinced that this will be a smooth process.”

Rainer Einenkel, head of the Bochum factory’s works council, told the news agency he’s determined to keep the factory open.

“We have binding contracts with Opel and General Motors, which protect us from plant closures and layoffs,” Einenkel said in an e-mail, adding that closure had been threatened on numerous occasions in the past. “It’s as simple as this: We will not let our factory be shut down.”

Jonas, who calculates GM stock is should be trading at $45 a share within a year, estimates the value of GM’s European operations at a negative $8bn. The automaker’s China business would be worth $10bn, he said.

“The negative value of GM Europe is almost as big as the positive value of GM China,” Jonas told Bloomberg News.