Oil companies will face the full force of the law if they manipulated prices, Britain’s energy minister said Wednesday as a ratings agency warned of massive fines if a European Commission probe into oil pricing finds wrongdoing.

The warnings came a day after the offices of Shell, BP and Norway’s Statoil were raided by investigators. Italian oil company Eni said the European Commission had asked it to provide information, although it was not under investigation.

“If it turns out to be the case that hard-pressed motorists and consumers have been hit in the pocket by manipulation in the market, the full force of the law should be down upon them. There is no doubt about that,” Britain’s Energy Secretary Ed Davey told Parliament.

A spokesman for Britain’s Prime Minister David Cameron said he expected companies to fully comply with the investigation.

London is home to some of the biggest trading desks in the oil business. After the Libor scandal — in which banks were heavily fined for rigging interest rate benchmarks — Britain approved legislation making it a crime to make false or misleading statements in relation to the setting of financial benchmarks.

“The investigation’s focus on potential collusion over price reporting draws parallels with the investigations by European and U.S. regulators into Libor rates,” the Fitch ratings agency said.

The European Commission has said it is concerned that companies might have colluded in providing distorted prices to a price-reporting agency to manipulate oil and biofuel prices. It also said companies might have prevented others from participating in the assessment process of a pricing agency, which it did not name.

Platts, the world’s largest pricing agency and a unit of McGraw Hill, is cooperating with the probe. On Wednesday, Antoine Colombani, the commission’s spokesman on competition policy, said only one pricing agency was involved in the probe.

“Even small distortions of assessed prices can have an impact on final prices, potentially harming consumers,” he said.

Fitch said that in the event of large fines, oil company balance sheets would probably be able to absorb the blow because of big cash reserves. The biggest settlement so far from the Libor scandal was the $1.5 billion that UBS agreed to pay to U.S., British and Swiss regulators.

“Other than fines, if an oil company is found to have distorted prices, it could face longer-term risks from damage to reputation,” Fitch said, noting that BP was excluded from some business in the Gulf of Mexico after the Deepwater Horizon disaster in 2010.

Sources and officials at the major trading houses Glencore, Vitol, Trafigura, Gunvor and Mercuria said they hadn’t been asked to cooperate with the probe.

The Swiss antitrust authority said no proceedings were underway as part of the E.U. probe. Switzerland is home to most global oil trading houses.

French oil company Total said no inspections had occurred at its offices. Last year, it wrote to regulators to question the way oil prices were determined, putting a spotlight on the pricing mechanisms of price reporting agencies.

The methodology designed by Platts for daily assessments of the oil markets is used to close deals worth at least $2.5 trillion a year.

Critics say the system is only a snapshot of the market and excludes most deals, making it vulnerable to manipulation. Supporters say it is the best mechanism so far devised to assess huge but often opaque markets.

Olivier Jakob of the energy consultancy Petromatrix said that the pricing system was far from perfect but that Platts remained the main reference for the entire market. “They are essential. . . . So if you were to close Platts tomorrow, you would have a very big problem,” Jakob said.

— Reuters