The four major supermarket groups have cut their petrol prices to below £1 per litre, with Morrisons, Tesco and Sainsbury’s also following Asda’s lead in introducing a price ceiling on petrol across their entire estates.

The latest skirmish in the price war was sparked by Asda which announced that it was cutting its prices by 2ppl on both petrol and diesel for a three-day period ending on Sunday December 13. This meant its prices were 99.7ppl and 103.7ppl.

Morrisons was next to react announcing that from Friday 11 December motorists filling up with unleaded at a Morrisons petrol station would pay no more than 99.9ppl. It added that it was cutting 1ppl off diesel.

Bryan Burger, Morrisons petrol retail director, said: “Today, for the first time in more than six years, we are moving unleaded prices down to below £1-a-litre.”

He said Morrisons would hold the price for as long as possible but it remained subject to changes in oil markets and foreign exchange movements.

Tesco than said that from midday on Friday December 11 the price of unleaded petrol would be 99.9ppl at all of its 500 filling stations, as well as 1ppl off diesel.

Peter Cattell, fuel director for Tesco, said: “We want to do all we can to help our customers in the run-up to Christmas. We know that our customers really value low fuel prices and that having unleaded for 99.9p a litre will really give customers a boost over the festive period.”

He said Tesco would continue to review the price of unleaded petrol subject to changes in oil markets and foreign exchange movements. Sainsbury’s later announced similar cuts would take effect on December 12.

Although Morrisons, Tesco and Sainsbury’s capped petrol prices across their full estates there was no indication that a similar restraint would be placed on diesel.