The European commission said its officers carried out "unannounced inspections" at several oil companies in London, the Netherlands and Norway to investigate claims they may have "colluded in reporting distorted prices to a price reporting agency [PRA] to manipulate the published prices for a number of oil and biofuel products".
The commission said the alleged price collusion, which may have been going on since 2002, could have had a "huge impact" on the price of petrol at the pumps "potentially harming final consumers".
Lord Oakeshott, former Liberal Democrat Treasury spokesman, said the alleged rigging of oil prices was "as serious as rigging Libor" – which led to banks being fined hundreds of millions of pounds.
He demanded to know why the UK authorities had not taken action earlier and said he would ask questions of the British regulator in Parliament. "Why have we had to wait for Brussels to find out if British oil giants are ripping off British consumers?" he said. "The price of energy ripples right through our economy and really matters to every business and families."
RAC technical director David Bizley said the allegations were "worrying news for motorists" who are already suffering due to the high cost of keeping a vehicle.
"Motorists will be very interested to see what comes of these raids. Whatever happens the RAC will continue to campaign for greater transparency in the UK fuel market and for a further reduction in fuel duty to stimulate economic growth."