The Cartel Office's decision affects mineral-oil groups DEA AG, Aral AG, Shell Transport & Trading Co., Esso, BP Amoco and Elf Acquitaine S.A. The ruling, which will take immediate effect, marks the culmination of months of investigations by the Cartel Office, and several rounds of court hearings.

The Cartel Office said it had found that the large oil groups were selling petrol to independent outlets at a wholesale price that was 12 pfennigs (Five U.S. cents or six European cents) per liter above the retail price charged by their own outlets.

This pricing structure made it virtually impossible for the independent outlets to turn a profit, the Cartel Office said.

"If independent competitors are squeezed out of the market, this will lead to a loss of competition in the medium to long term. Ultimately, consumers will suffer," said Cartel Office president Ulf Boege.

Mr. Boege said that although the ruling would not in itself be sufficient to guarantee that independent outlets would be able to cover costs, at least they would no longer find themselves in the position of having to sell petrol at below the cost price. Some 20% of Germany's 16,000 petrol stations operate independently of the major oil groups.

Germany's oil giants expressed shock and dismay at the ruling and pledged to launch an appeal.

"We consider the ruling to be grotesque and unlawful," said Wolf-Ruediger Grohmann of BP Deutschland in Hamburg.

He described the ruling as impracticable, inconsistent and flawed.Deutsche Shell said that the ruling represented an "intervention in the market economy, unparalleled in German history."

The group said it plans to take all legal measures at its disposal against the ruling, which it called indefensible. Aral, DEA and Elf said that they, too, planned to appeal against the decision.

Meanwhile, the federation of mid-sized petrol stations, Uniti, welcomed the decision, saying that it sent out a "very positive signal and a glimmer of hope for an end to the price war among petrol stations."

However, the federation of independent petrol stations stressed that its members had yet to derive any commercial benefit from the ruling.

The fierce price war that is currently raging on Germany's petrol market was triggered in March, when oil group DEA launched its "Payback" discount card, cutting petrol prices by one pfennig per liter. All of Germany's major service-station groups found themselves sliding into the red in their effort to undercut each others' prices.

It was this development that prompted the independent service stations - which, because they do not enjoy the strong financial backing of the oil giants, were left behind in the price wars - to file a complaint with the Federal Cartel Office.