Victims of contaminated petrol will be able to claim the cost of repairs to their vehicles on their insurance.

Thousands of cars in south east England have broken down after being filled with what is believed to be suspect fuel purchased from Tesco and Morrisons supermarkets. Trading standards officials discovered silicon traces in the petrol.

Silicon compounds, a common lubricant in the petrochemical industry, can foul oxygen sensors that monitor exhaust gases as part of modern engine management systems. The sensors control fuel injection to the engine and, when damaged, make the engine misfire or stop.

The problem has been traced to a batch of unleaded fuel from Vopak distribution terminal in West Thurrock, Essex.

Norwich Union, NatWest, Royal Bank of Scotland, Direct Line, Churchill and Liverpool Victoria said they will pay out for accidental damage on comprehensive motor insurance policies.

However, if you stop driving when the engine warning light on your dashboard first comes on, Ian Crowder from the AA explained: "by the time you have paid the excess on your car insurance policy and lost your no claims bonus, it is probably not worthwhile claiming on your car insurance because the cost of repairing the oxygen sensor may only be a couple of hundred pounds.