Independent retailers have reported a surge in demand for unleaded as motorists shun the supermarkets in the wake of the tainted fuel furore.

However, some have expressed concerns as to how the multiples will react once they start trying to woo their customers back. And PRA director Ray Holloway has warned retailers to think very carefully about compromising their margin should the supermarkets slash their prices.

Independent sites in the south east have been selling as much as double their normal volumes of unleaded, with some rationing fuel to ensure they can meet demand.

Cambridgeshire-based Jonathan James, who runs a forecourt within a mile of a Tesco site, ran out of standard unleaded for five hours today (Monday), despite limiting his customers to £30 worth of fuel.

He said: “We’ve seen a massive increase in trade. We’ve been rationing fuel at two of our three sites since Friday morning and will continue to do so until we can get a handle on the situation.

"We’ve held our prices back until today, despite everyone around us putting up theirs. Although crude oil prices are going up, I felt it would be seen as profiteering.

“My major concern is how the supermarkets will react, because they won’t take this lying down. What will they do to try and regain the trust and the lost trade?”

Harvest Energy, which supplies fuel to Tesco, Morrisons and Asda, has said that unusually high levels of silicon were found in four storage tanks at the Vopak terminal in West Thurrock, Essex.

The company said that standard testing ensures that its petrol reaches the European and British specification BS EN 228 for unleaded fuel. However, this does not include a routine test for silicon, meaning its presence was not detected prior to sale. “We will now be testing for silicon as a matter of course,” a company spokesperson said.

Meanwhile, PRA director Ray Holloway has criticised Trading Standards for not acting more promptly. “Trading Standards stood back and disengaged for too long. I wonder if an independent forecourt operator would have been treated equally had their fuel tanks been suspected of dispensing contaminated fuel?,” he said.

He added: “The retail pump price will undoubtedly come under scrutiny as consumer confidence recovers, that’s certainly true for the supermarkets but less so for traditional forecourt businesses. The former sector have an interesting dilemma that may prove very testing if they are to find a short term solution; how can they use price as a weapon when some motorists consider cheaper petrol is the underlying cause of the fuel quality issue? I expect them to try price and a promotion. Independent forecourt owners should, however, think very carefully before cutting their margins and abandoning a price that will cover all their costs.”