Germany's competition watchdog, the Federal Cartel Office (FCO), is set to launch an inquiry against five major petrol companies for allegedly trying to drive independent petrol stations out of business through illegitimate pricing practices, said AFP.

"The Federal Cartel Office has launched a procedure against five petrol companies - Deutsche BP/Aral, ExxonMobil Europe/Esso, ConocoPhilips Germany/Jet, Shell Deutschland, Total Deutschland - on suspicion they tried to obstruct independent filling stations," the watchdog said.

According to Reuters, the companies have been accused of selling fuel for less than the wholesale price at strategic locations surrounding independent operators in a bid to reduce their businesses, while Total and Shell were also charging independent filling stations more for wholesale petrol than what they charged motorists at their own station.

"To compete with the oligopoly of the five major companies, independent filling stations must be supplied at fair prices," said FCO president Andreas Mundt, as cited by MarketWatch.

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The investigation will "help strengthen competition from independent service stations against this oligopoly" added Mundt, who also assured the public that the investigation was "a signal to the big five that we take these allegations seriously."

Unsurprisingly, some of the accused companies have come out with statements protesting their innocence.

BP said in a statement: "In our opinion these claims are unfounded. The German Cartel Office has merely requested some information from us - this does not imply that there has been any violation."

A spokeswoman for Exxon Mobil added that "it is ExxonMobil's policy to always comply with the law" and "we will support the cartel office and send it the relevant facts."

This is not the first time that German anti-trust authorities have had to monitor the major oil companies over their pricing practices.

"It's a continuous process, but it's not easy because prices fluctuate constantly," said a spokesman for the FCO.

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"We've done a lot of preparatory work before taking this move and the five companies now have to respond and submit documentation by a certain deadline," he added.

A spokesman for Total though questioned whether the whole investigation procedure was necessary.

"Of course we will cooperate," he said. "[But] I wonder how the cartel office will explain to motorists - who are constantly complaining of rising prices - that we're being accused to offering prices that are too low."