Three of Britain's major supermarkets began a petrol price war on Tuesday and cut fuel prices by up to five pence a litre, a move that could ease inflation in August.

Soaring petrol prices helped push Britain's inflation rate to nearly double the central bank's 2 percent target in June, preventing the Bank of England from cutting interest rates to boost a slowing economy.

George Buckley, chief UK economist at Deutsche Bank, said that assuming petrol prices fell by around 3.5 percent, the inflation rate could fall by around 0.15 percentage points in August.

Asda said unleaded petrol would fall by three pence to 113.9 pence a litre at its 170 forecourts. The diesel price will fall to 128.9 pence.

Morrisons said it would cut petrol and diesel prices by four pence a litre, while Sainsbury's said customers who spend 50 pounds or more in-store would get a five pence a litre discount on fuel during a promotion starting on Thursday.

Asda's trading director David Miles said the cuts were in response to the recent drop in oil prices on the global market.

"We are seeing a more stable reduction in oil prices allowing us to pass on the savings to customers," he said in a statement. "We urge other retailers to follow our lead at a time when customers need as much help as possible."

Surging demand from emerging economies in Asia has helped drive a sixfold rise in oil prices since 2002, but concerns over flagging demand in the United States and other large consumers have cut prices in recent days.

The average price of a litre of petrol in Britain in July was 119.5 pence, compared with 104.3 pence in January, according to the AA motoring organisation.

Retailers have come under pressure from consumer groups to reflect the falling oil price in their petrol prices.

Morrisons said it had cut prices at its 285 petrol stations.

Last week, the government postponed a rise in fuel duty planned for October for at least another six months because of soaring world oil prices and a bid to keep down the headline rate of inflation.

The Treasury said delaying the increase was also consistent with the government's commitment to support the Bank of England in maintaining low inflation.

A survey last month found that drivers have cut the number of journeys they make by car to try to save money.

A third said they no longer drove to the local shops, while nearly a quarter have stopped using the car on the school run, according to the Populus poll in the Times.