The price of a litre of unleaded fuel has reached £1.40 at a garage in the South East, sparking fears of a fuel emergency.
Campaign group Fair Fuel UK said a BP garage in Kent was charging 140.9p per litre, which is thought to be the highest price recorded so far.
A litre of diesel at the forecourt on the M2 near Rainham, Gillingham, was being sold for 144.9p per litre.
The average price for petrol in the UK last month was 128p per litre for unleaded, and 133.38p per litre for diesel - already expensive enough when other costs of motoring, such ascar insurance and road tax, are factored in to people's budgets.
Peter Carroll, spokesman for Fair Fuel UK, said the prices seen at the forecourt in Rainham were "shocking".
He added: "My reaction to these prices is one of horror, of what it will do to the economy, what it will do to people and what it will do to business. They will be crushed by this.
"We are being pushed into a fuel price crisis."
The findings on fuel prices come as Chancellor George Osborne delivered a strong hint that a 1p fuel duty hike due next month will be scrapped amid fears over soaring oil prices.
"When it costs £1.30 for a litre of petrol, £80 to fill up a family car, I know people feel squeezed," he said.
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