Motorists are to see a further fall in the cost of filling up after three of the UK's major supermarkets stepped up their forecourt price war.

Sainsbury's and rival Asda are to cut the price of diesel by up to 2p a litre and unleaded petrol by a penny.

Tesco, which is Britain's biggest petrol retailer with about 500 petrol stations, will cut unleaded petrol by 1p per litre, with diesel reducing by at least 1p a litre although some sites will get a 2p a litre price cut.

The moves follow a decline in the price of crude oil, which is now below 90 US dollars a barrel due to weaker global demand.

This means motorists are benefiting from some of the cheapest prices for over three years, although some of the benefit of Brent crude's recent decline has been offset by a strengthening in the US dollar.

Supermarkets have been slashing forecourt prices as part of their wider effort to win back grocery customers from discount rivals Aldi and Lidl.

Asda, which has 232 forecourts, said its customers will pay no more than 126.7p a litre for diesel and 123.7p per litre for unleaded petrol.

The supermarket's petrol trading director Andy Peake said: "We're giving drivers the opportunity to fill up their cars with some of the cheapest fuel prices in the market for years.

"No matter where customers live they will benefit from the same fuel price with our national price cap."

The AA said a typical 50 litre tank of unleaded petrol now costs around £2.50 less than it did a year ago and a 55 litre tank of diesel is around £4 cheaper.