The number of theories about how the petrol came to be contaminated was beaten only by the number of motorists who were stranded or had to nurse their cars home yesterday.

Reports of breakdowns came from as far north as Newcastle, Glasgow and Dundee despite the dirty fuel being sold only in the South East and Midlands.

As mild hysteria set in among motorists, with at least two reports of contaminated petrol in Belfast, the rumour mill went into overdrive.

Bioethanol was the first potential villain to be cited, quickly followed by diesel from an unwashed storage tank and then water, silicon and iron filings. But, while the experts attempted to pinpoint the cause, drivers continued to find their cars juddering to a halt or kangarooing their way home.

Sanjay Mistry told yesterday how her car was no longer running smoothly. Her Renault Clio spluttered up the A1, its engine misfiring with regular shudders that infuriated its owner. Ever since Ms Mistry, of Farnham, Surrey, stopped for petrol at a supermarket chain at the weekend, her vehicle has not been the same.

“As I reached closer to home, I felt that the engine was running less smoothly,” she said. “All through this week, my engine misfires and judders. I hope it’s an easy fix.”

She is not alone. Thousands of motorists have experienced poor performance from their cars after filling up with petrol at supermarket forecourts.

Afflicted engines have been “kangaroo-hopping”, shuddering and even shutting down completely.

Frustrated drivers headed en masse to garages, where forecourts were crowded with cars awaiting repairs — and the relevant parts. Service centres gave warning that customers may experience delays in repairing their vehicles as mechanics worked overtime to meet demand, and suppliers struggled to find spare parts.

Poole’s Peugeot repair centre in Gosport, Hampshire, resembled the automotive equivalent of a doctor’s surgery, its garage filled with vehicles that had coughed and spluttered all week. Dan Draper, service manager, said that he had repaired more than 20 vehicles.

“The engines are cutting out, the cars are sluggish. We’re fixing several a day above our normal workload but we’ll get it done,” he said.

Mr Draper said that most customers were asking for fuel samples so that they could claim back the damages from supermarkets. “They are pretty unhappy. Most people haven’t got a spare £300 and that is what this is costing them.”

Garages throughout the South East were running out of parts, including the oxygen sensor in engine management systems that were affected by faulty petrol. Scott Perry, owner of S Perry Mechanical in Northampton, said customers had complained about their cars misfiring and that one engine was completely destroyed.

Angry motorists called on the supermarket chains to take responsibility for the damage.

Karen McKelvey, a driving instructor from East London, said that she had lost £400 in income since her Vauxhall Corsa broke down after she filled it up at a Tesco forecourt.

She was unable to go to work because her car was in a garage for three days. “Tesco should compensate us for this problem. If they don’t, I will be shopping elsewhere,” she said.

Graham Brown, of Burwell, Cambridgeshire, said that his wife’s Range Rover had been behaving strangely since it was filled with petrol. Mr Brown said: “After filling last time it has what appears to be a lack of power and juddering. It was only serviced 750 miles ago.”

What those affected should do

-Motorists whose cars are damaged by defective petrol have a right to compensation under the Consumer Protection Act 1987 -if they can prove who was at fault

-Petrol stations have “an absolute duty” to provide customers with nondefective fuel, lawyers say

-Martyn Day, product liability lawyer at Leigh Day & Co, says that the onus would fall on the retailer to pay compensation even if it was unaware of the problem, or if another party — for instance the petrol manufacturer — was at fault

-Although the chances of cars of varying ages and conditions malfunctioning within a short space of time are small, the fact that most of them bought fuel from the same batch is not sufficient evidence to establish that the fuel is to blame

-Since this is a civil matter, motorists will need to establish only that “on the balance of probabilities” the fuel caused the damage

-Therefore, a credible mechanic who has examined the car needs to say only that in his expert opinion it is more likely than not that the fuel was to blame

-Consumer groups say that motorists who think that their vehicle has been affected should have it tested and keep their petrol receipts

-At least one insurer, Liverpool Victoria, has said that its policies will cover damage from defective fuel

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