The Prime Minister's spokesman said regulators should examine any evidence of oil price-fixing "very carefully", after the Daily Telegraph revealed fears that banks and traders are likely to have fiddled the oil market.
Concerns are growing about the reliability of petrol prices because a report for the G20 found the market is wide open to "manipulation or distortion".
Traders from banks, oil companies or hedge funds have an "incentive" to distort the market and are likely to try to report false prices, the official report said.
Politicians and fuel campaigners are urging the Government to expand its inquiry into the Libor interest rate-fixing scandal to see whether oil prices have also been falsely pushed up.
Any efforts to rig the oil price would affect how much drivers pay at the pump, which soared to a record high of 137p per litre of unleaded earlier this year.
Quentin Willson, a motoring expert at FairFuelUK said any "deliberate fiddling of the figures by financial institutions and traders will have cost UK consumers millions in unnecessary expenditure."
"These dark and devious forces should be held to account and an investigation into oil price manipulation started immediately."
Should there be an inquiry into whether the oil rate was rigged?
Robert Halfon, who has led a group of 100 MPs calling for lower fuel prices, also called for the matter to be investigated, saying it: "needs to be looked at by the Bank of England urgently".
Paul Tucker, the Deputy Governor of the Bank of England, has suggested other markets should be looked at by investigators, after Barclays was fined £290 million for fixing Libor.
A Number 10 spokesman today said it was important the oil market is seen to be "fair and efficient".
"It is a matter for regulators," the spokesman said. "With the Libor scandal, that is something that the FSA decided to look at because they had evidence.
"The important thing is that we have efficient and fair markets. And if there is evidence that any market is being manipulated then that is a matter for the regulators, and those regulators should look at it very carefully."
"It is important because people in the market rely on these things being accurate."
Copyright 2012 Telegraph Media Group Limited. All Rights Reserved.
(Originally published July 16, 2012, on telegraph.co.uk.)