Petrol prices have hit their lowest levels of the year in some areas of the UK, but the differential with rural areas that have the highest prices is growing, according to the AA.

Its monthly Fuel Price Report shows that the average price of unleaded petrol in the UK edged above 130ppl at the end of April, and continues to hover around that level.

However, a war where supermarkets have pitted vouchers against rock-bottom pump prices means the cheapest petrol in many big towns and cities is at a year low of just under 126ppl.

But in small rural towns where major supermarket competition is less fierce or there is only one supermarket, the price gap between them and cheaper major towns has started to grow again to 4ppl.

Although the differential is still less than last-year’s 5ppl or 6ppl excesses, the AA predicts the £2-a-tank difference for small cars and £2.80 for a Mondeo-sized vehicle will make more drivers re-route their trips to take in the cheaper forecourts.

In its analysis it says a 2ppl rise in the wholesale price of petrol since early March could explain the price rise. However, with the north-west European wholesale price of petrol back below $1,000 a tonne after a month above, and the pound worth nearly $1.70 last week, it expects the pressure on retailers to put up prices to fall away.

“Whereas supermarkets, faced recently with worse sales figures when fuel is factored in, have held their fire on pump price increases in cities and major towns, there are signs that some of them and other retailers are getting price-trigger happy again in rural towns,” said AA president Edmund King.

“A 2ppl increase in the wholesale price of petrol through March into April may justify that but, if pump prices stay higher while costs continue to fall back, rural town drivers will be tempted to look elsewhere for cheaper fuel.”