Motorists filling up at Asda and Morrisons forecourts will pay under £1/litre for petrol

The Asda price drop, falling by 2p/litre to 99.7p/litre for unleaded, will last three days from today, while Morrisons says it hopes to keep its everyday price of 99.9p/litre for "as long as possible".

The supermarkets' move means the price of unleaded has hit a six-year low and comes just days after the RAC predicted prices would fall below £1/litre before the Christmas getaway.

As Asda sets a national price cap across its 277 forecourts, drivers will pay no more than 99.7p/litre for unleaded and no more than 103.7p/litre for diesel from today until Sunday 13 December.

From Monday, the price will go back to 101.7p/litre on unleaded and 104.7p/litre on diesel. An Asda spokesperson says the temporary fuel price cap wasn't a loss leader – a pricing strategy to entice customers in to potentially purchase other, more expensive products – but part of its "customer-led festive pricing regime" that began with its decision to pull out of Black Friday.

Drivers heading to any of Morrisons' 336 forecourts will also see the cost of unleaded fall to 99.9p/litre. Usually Morrisons "prices locally", which means petrol prices vary regionally, but it says it's capped prices nationally, so drivers filling up across any of its stations will pay no more than 99.9p/litre for unleaded.

It's also cutting the price of diesel by 1p/litre from today, but it hasn't set a national price cap on diesel so pump prices will vary regionally. Morrisons adds that motorists will have saved an average of £17/week since the petrol price peak four years ago.

While today's price cuts are a boon for motorists, check the website Petrolprices.com to find the lowest price in your area and see our Cheap Petrol and Diesel guide for more ways to save when filling your tank.

According to Petrolprices.com, the average UK price for a litre of diesel was 108.88p/litre on Wednesday, while the cost of unleaded petrol stood at 106.34p/litre.

Additional reporting by the Press Association.