Supermarkets have increased the price of petrol and diesel every day since the end of March, a new analysis shows.
More than eight pence per litre was added to average pump prices between March 26 and May 23 at the big four supermarkets, RAC Fuel Watch data shows.
The rises are due to the price of oil increasing to more than 80 US dollars, combined with a weakening of the pound.
Average UK forecourt prices currently stand at £1.26 per litre for unleaded and £1.30 for diesel.
This is the most expensive both fuels have been since October 2014.
RAC fuel spokesman Simon Williams said: "This is the worst series of consecutive daily supermarket price rises we have seen since we began monitoring this three-and-a-half years ago.
"The supermarkets are being very quick to pass on increases in the wholesale price of fuel. They are far faster at passing on rises than falls.
"The outlook for fuel prices in the weeks ahead is not good, with another penny a litre expected to be added.
"All we can do is hope the international forces - which have caused the oil price to rise - ease and take the heat out of prices on the forecourt."