A burgeoning petrol price war has escalated after Sainsbury's became the third supermarket to cut fuel costs.
The store said it was cutting 5p a litre from fuel from Thursday for customers who spent more than £50 or more in its shops, in a promotion which will run for two weeks.
Asda began the price cutting by taking 3p off a litre, bringing the price of petrol down to 113.9p a litre and diesel down to 128.9p .
Morrisons swiftly responded by cutting prices by 4p a litre. Both companies said they were responding to a recent drop in the price of oil, which has seen the cost of a barrel drop from a peak of $147 to around $130.
Asda said all 170 of its petrol forecourts across the country would sell fuel at the cheaper price. David Miles, the store's trading director, said: "We are seeing a more stable reduction in oil prices, allowing us to pass on the savings to customers.
Morrisons group store operations director Mark Gunter added: "The cost of crude oil and refined product has fallen in the last few days and we are ensuring our customers reap the benefit by passing on the saving quickly, for cheaper prices at the pumps."
Tesco has already offered a five pence a litre discount to customers who spend £50 in its supermarkets and is now expected to match local branches of other supermarkets rather than lose business.
Edmund King, AA president, said: "Asda's petrol price drop is excellent news for UK motorists and we urge other fuel retailers to reduce their prices – and not only where they find themselves neighbouring an Asda petrol station.
"We have seen two drops in European wholesale fuel prices so far this summer with the UK motorist seeing next to no benefit. Since mid July the wholesale gasoline price has fallen 6 per cent and the AA expects fuel suppliers to pass on, not pocket, the saving for the good of UK families, hauliers and the economy.
"We will watch price movements like a hawk, and should fuel suppliers and retailers appear to be dragging their feet we will seek to expose this."