Berlin/Ruesselsheim - Thousands of workers employed by General Motors in Europe took to the streets Thursday to demonstrate against the giant US carmaker's sweeping restructuring plans and to save their jobs.

The protests came as GM's German offshoot Opel prepared to unveil a rescue plan for the German operations and the government in Berlin stepped up its criticism of the US-based auto group amid a deepening crisis in the global car industry.

German Economics Minister Karl-Theodor zu Guttenberg lashed out Thursday at the Detroit-based GM criticising the company for failing to provide adequate information about its future plans for Opel, which has a corporate history dating back to the late 19th century.

The German Economics Minister said up until now both potential investors and the German Government still did not know what the GM group planned for Opel, which is expected to unveil the new business plan possibly on Friday.

Opel hopes the plan will pave the way for Berlin to provide the struggling carmaker with about 3.3 billion euros (4.3 billion dollars) in government-backed loan guarantees to help it through the current downturn in the car market and lead it to breaking away from GM.

"Spinning off (from GM) is the only chance," Klaus Franz, the chairman of Opel's workers' council told the 15,000 workers who has turned up for the rally outside the group's German headquarters in the western city of Ruesselsheim.

The battle to save Opel and the jobs of its 25,000 workers comes as Germany's political parties gear up for an election set down for September.

Speaking at Thursday rally in Ruesselsheim, German Foreign Minister Frank-Walter Steinmeier, who is to head up the Social Democrats election campaign, said GM had done well out of Opel for a long time.

"Now the European operations face being disposed of like a squeezed out lemon," said Steinmeier.

But in comments at a meeting of the German Foreign Press Association in Berlin, Chancellor Angela Merkel again insisted that government support for Opel and the auto spare parts group Schaeffler, which is also seeking state aid, was dependent on the groups producing viable business plans.

"Only if you have a viable restructuring plan, which in the case of GM and Opel is particularly difficult because of integration of the two groups, can you decide what type of assistance is needed," said Merkel.

Merkel also went on to indicate that the government was likely to give priority to back financial guarantees rather than additional state aid.

Adding to the pressures building on GM and Opel, GM announced in Detroit that it had run a 30.9-billion-dollar loss in 2008 after a daunting fourth-quarter loss of 9.6 billion dollars. Opel booked a pre-tax loss of 1.6 billion dollars (1.25 billion euros) last year.

But the European Commission warned Thursday that it would take action to head off countries providing what it considered to be unfair support to their national car sectors.

This is the second time in the last five years that Opel has faced a major shakeout in its business with the company cutting 10,000 jobs in 2004 after GM launched another major overhaul of its global operations.

Now only a few months after Washington lent GM and rival Chrysler 17.4 billion, GM is proposing another far-reaching restructuring plan, which includes big job cuts worldwide and could result in its hiving off parts of its international operations.

In addition to Germany, GM has operations in Britain, Spain and Sweden. However, GM's Swedish SAAB company has already filed for bankruptcy protection.

German carmakers including Volkswagen, BMW and Daimler, the manufacturer of luxury Mercedes-Benz cars have already cut production and placed employees on reduced working hours as they face up to the global economic slowdown. (dpa)