Motorists paid 11p more per litre for petrol in May than February as pump price increases rolled on for a fourth month.
Figures released by the RAC show average petrol pump prices rose from £1.20 per litre in February to £1.31 in May. Diesel prices increased on average by 7p in the same period, to £1.36 a litre.
May's increase was due to a weakened pound and rising wholesale prices, the RAC says.
But oil prices fell towards the end of the month, so forecourts could be set to cut prices in the coming weeks.
RAC fuel spokesman Simon Williams said: "May was another miserable month for drivers with the fourth straight average price rise of both petrol and diesel taking us near to a five-year high.
"Luckily though, oil closed out the month 9% lower at 65 US dollars, which should soon translate to lower prices at the pumps.
"After suffering a steady flow of daily fuel price increases because of rising wholesale costs, we urge retailers to reflect this sudden drop in the price of oil by cutting their prices as soon as possible.
"The supermarkets who buy fuel more often than smaller retailers due to the large volumes they sell should be able to do this straightaway to bring some welcome relief to drivers who have had to endure seemingly ever-increasing prices."
