BRITAIN'S biggest supermarket chain is facing legal action from motorists who say a fuel pump mix-up has cost them a fortune in engine repairs.

Tesco has denied claims that a diesel fuel pump at its filling station in Newton Aycliffe was dispensing petrol. But drivers who filled up say their vehicles have been damaged by contaminated fuel.

In one case, a motorist says he has been left facing a bill for £1,500 to get his Mercedes back on the road.

Derek Wood, 61, said his car ground to a halt within 25 miles of filling up.

His insurer, NFU Mutual, is seeking to claim the cost of the engine damage back from Tesco, but the supermarket maintains it is not to blame.

Officials say that if the pump had been dispensing petrol instead of diesel many more drivers would have complained.

However, other motorists have come forward to say their vehicles suffered a similar fate, and the store chain now faces the prospect of court action.

Sharon Heathcote, 30, a community nurse from School Aycliffe, said her Nissan Micra diesel had fuel problems after a visit to the petrol station.

Her car broke down a few miles after filling up and her garage told her the car had petrol, rather than diesel, in the tank. It required a new fuel injection system, costing more than £3,000.

She told the supermarket in a letter that she was prepared to take the matter to court.

Tesco told her no one else had complained.

When Mr Wood's insurers wrote to the supermarket they received the same response.

Mr Wood said last night: "We are quite prepared to take it to court."

Tesco replied, again saying that no one else had complained.

Miss Heathcote said: "It has cost us nearly £4,000 to fix the car, including hiring another one while ours was repaired.

"We have three small children and have just moved house and for us, financially, this is a big thing."

A local paper has also published an open letter from another driver claiming to suffer the same problem.

Tesco said last night that it had received "four or five" complaints but maintained there was no problem with the pump.

A spokeswoman said: "These four or five complaints have been spread over the past six months.

"Trading standards checked our fuel in July after the first complaint was received and it was found to be clear.

"They came in again last week following the latest complaint, and we are awaiting the results.

"However, this is an extremely busy petrol station and if there was a real problem we would expect to have received many more complaints."