Oil groups caught price fixing will face the “full force of the law” and “heavy fines”, Ed Davey said on Wednesday as the UK energy secretary responded to concerns that hard-pressed motorists may have been overpaying for petrol for the past decade.

Mr Davey, addressing MPs in an emergency statement in the wake of the European Commission’s raid on oil groups on Tuesday, said the government was “deeply concerned” about the issue.

“These investigations are at an early stage and the commission has made clear that the investigation does not imply guilt until the facts are clear,” Mr Davey said. “If it turns out to be true and hard-pressed consumers have been hit in the pocket, the full force of the law will be felt.”

His comments came after Europe’s leading antitrust authority raided oil majors Royal Dutch Shell, BP and Statoil in an investigation into the setting of oil prices.

However, it is not known whether the alleged price fixing led to higher or lower prices at the pump.

The companies involved said they were co-operating with the authorities.

The probe into the oil benchmark comes in the wake of the scandal over the manipulation of interbank Libor rates and months after one of Europe’s largest energy trading groups warned of “inaccurate pricing” of crude and oil products.

Mr Davey said he did not know how long the probe would take or whether or not consumers might be compensated should fines be levied. “These are very early days in the investigation, these are only allegations and we should not jump the gun,” he said.

But MPs were angry with Britain’s Office of Fair Trading for not picking up on alleged price fixing in a recent inquiry. In January, the competition watchdog concluded that the UK fuel market was operating fairly and did not warrant a Competition Commission inquiry.

Robert Halfon, the Conservative MP for Harlow, hit out at the OFT for its “limp-wristed lettuce leaf-type inquiry” as he demanded prison sentences for those involved should the allegations prove true. He also told Mr Davey that any money levied in fines should be used to cut fuel duty for motorists.

The companies are suspected of distorting the price of oil since 2002. During that period the cost of petrol in the UK has become a sensitive political issue as consumers have watched the price of fuel rise more than 80 per cent to about 135p a litre.

This week, the government said it would make service stations display the price of their fuel on motorway signs to help drivers avoid excessively high prices on long journeys, under plans being drawn up by Downing Street.