Motorists will get a boost this weekend as Asda, Morrisons, Sainsbury's and Tesco will cut both unleaded and diesel prices by up to 2p a litre from tomorrow.

Prices vary locally at Morrisons, Sainsbury's and Tesco forecourts, but Asda says motorists will pay no more than 131.7p per litre for unleaded and no more than 135.7p per litre for diesel at its pumps from tomorrow (see our Cheap Petrol and Diesel guide to drive down costs).

Today's move is the latest in a line of recent price drops made by the big four supermarkets. But the latest reductions won't necessarily mean any of these supermarkets will be the cheapest fuel provider. The website lists the cheapest in your area.

Unleaded prices have risen over the past few months from an average 132p a litre in December, to 140p a litre in March. But earlier today, before the supermarkets announced their price drops, the AA said average unleaded prices could fall to about 134p a litre soon, thanks to wholesale fuel prices falling.

Supermarket cuts already helped push the average price of unleaded to 136.64p per litre on Wednesday, with the big four all cutting the price of unleaded at the pumps (see our Asda, Morrisons, Sainsbury's and Tesco cutting petrol prices MSE News story). This average price is 3.27p lower than a month ago.

Average diesel prices have fallen 4.94p to 141.44p over the past month, according to the motoring group.

AA president Edmund King said: "In the past 12 months, oil and fuel price speculation has swung back and forth through the fuel market like a wrecking ball, smashing family budgets, pulverising fuel demand, and rocking the foundations of fuel retailer and other business viability.

"At least, though, the current prices are going in the right direction, giving drivers a breath of optimistic spring air."

Additional reporting by the Press Association.