Petrol prices are set to plunge to a four-year low this weekend, with supermarket Asda knocking 2p off a litre.

The Asda cut, effective from tomorrow, will take its petrol down to 112.7p a litre - the cheapest since October 2010.

Asda is also reducing its diesel by 1p a litre, taking the price to 118.7p a litre.

Amid failling world oil prices, Asda and other supermarkets have introduced a number of fuel reductions over the last few weeks, including some during the last few days.

Asda's petrol was as high as 126.7p a litre on September 28 this year so will have dipped 14p a litre by the time tomorrow's cut comes into effect.

Asda's petrol trading director, Andy Peake, said today: "We know how important it is to pass savings back into motorists' pockets as soon as oil prices fall, which is why this is our 10th price cut since September."