Although the average price of petrol and diesel on the UK’s forecourts fell slightly in August, retailers failed to pass the entire discount in the wholesale price of unleaded to drivers, data from the RAC has found.

The RAC has since suggested drivers should be ‘angry’ at the low petrol price drop.

A litre of petrol reduced 0.27p to 128.88p but the wholesale price came down dramatically by 4.38p to 96.57p.

RAC fuel spokesman Simon Williams said: “Drivers have the right to feel angry that the price of fuel did not fall more in August than it did.

“With nearly 4.5p coming off the wholesale price of petrol drivers should have seen, at the very least, 2p a litre being knocked off at the pumps by the end of the month.

“While the average price charged by the supermarkets came down a little more than the UK average they should really have led the way with larger cuts which would have spurred other retailers to reduce their prices too.”

Each litre of diesel decreased by 0.38p to 131.66p while its wholesale price fell by 1p a litre to 101.12p.

This means the cost of filling a family-sized 55-litre car came down by 15p to £70.88 for petrol drivers and 21p to £72.41 for diesel cars.

The average price for petrol at the country’s four biggest fuel retailers – Asda, Tesco, Sainsbury’s and Morrisons – was 125.41p (a reduction of 0.55p) and 128.04p diesel (0.6p saving on July).

Both fuels are around 3.5p cheaper at supermarkets than other UK fuel stations.

The minor price decrease comes at a time in which data from the RAC recently showed that both diesel and petrol prices increased during July as the pound lost 3% on the dollar.