Motoring organisations urged the Government to shield motorists from rising petrol prices after the price of crude oil rose to new records.
The AA and RAC warned that Chancellor Gordon Brown may have to consider postponing the annual rise in fuel duty for cars beyond September 1, when it is due to increase by 1.2p per litre, if oil prices remain at their current highs.
In Wednesday's Budget, Mr Brown deferred the rise until September in a bid to win over Britain's motoring voters.
The motoring groups warned that the soaring price of crude risks pushing petrol prices back to levels last seen during the fuel protests in 2000.
The cost of a barrel of US light crude hit a fresh record yesterday, rising by 73 cents to $57.19 in afternoon futures trading.
London's Brent crude topped $55 for the first time, trading at $55.85 a barrel this morning.
The rises came despite Opec's decision on Wednesday to lift output, with analysts warning that the oil cartel still may not be able to pump enough to meet demand.
Richard Slape of Seymour Pierce said Opec may succeed in bringing the cost of oil below $50 a barrel in the short term.
But he added: "We doubt if consistently lower prices are achievable without significant new investment to increase production capacity."
The AA said its research had shown that the average price of a litre of unleaded petrol had reached 80.5p, while diesel cost
84.9p a litre. The average price in the highly competitive supermarket petrol market had hit 79.3p a litre.
The AA's Paul Watters warned a rise in the average supermarket price of unleaded above 80p a litre would risk a repetition of the anger that led to the fuel protests in 2000, when the price of unleaded hit a peak of 85p a litre. "Gordon Brown has shown he can help by delaying increases, but we still need fuel duty to be lower," Mr Watters said.
An RAC spokesman said that while the UK had the cheapest petrol in Europe before tax, duty accounted for about three quarters of the forecourt price of a litre. He said the RAC welcomed Mr Brown's decision to defer the increase in fuel duty until September 1.
But he added that Mr Brown was basing his case for a rise in September on the assumption that oil prices would have significantly fallen by then, which "remained to be seen".
The rise in oil prices forced Opec to consider a second output increase just a day after its deal to raise supplies failed to halt crude's record-breaking advance.
With its output already near a 25- year high, Opec is stretched to meet rapidly rising demand, leaving investors betting that oil's bull run has further to go.