Supermarkets began a petrol price war yesterday, bringing relief for millions of motorists in response to a fall in oil prices. Asda announced a cut in the cost of unleaded and diesel by 3p a litre, a move that triggered Morrisons’ 4p a litre reduction for unleaded petrol and diesel.

Sainsbury’s followed suit with a two-week promotion offering a 5p per litre reduction for customers spending £50 or more in its stores, while Tesco said it was lowering prices by up to 4p a litre.

BP, the owner of 223 petrol stations across the UK, said it would reduce prices by an average of 1p per litre.

Edmund King, president of the AA, said the cuts showed the fuel “spike” had reached a plateau.”If the global oil price drops further we could see even bigger reductions,” he said.

The RAC said this week that the number of breakdowns caused by the siphoning of fuel from vehicles had more than doubled since the start of the year.

The global oil price has fallen 6% since it reached a mid-July peak of $147 per barrel and fell below $130 per barrel yesterday.

David Miles, Asda’s trading director, said: “We are seeing a more stable reduction in oil prices, allowing us to pass on the savings to customers.”

BP said if the global oil price continued to fall “obviously” prices would be reduced further. But the oil giant added that it did not control pricing at the majority of its branded petrol stations because 950 of its UK stations were run as franchises.

The cost of fuel for a car has soared over the past 12 months, with the average price of petrol rising by a quarter to 119.42p a litre. An outcry from motorists persuaded the government to shelve a planned 2p increase in fuel duty that was due in October