The RAC has said drivers should feel angry that filling stations around the country have not passed on significant savings on the cost of petrol in the last month.
The latest RAC Fuel Watch data shows that there was a small reduction in average costs around the country in August but this did not reflect the larger wholesale savings.
On wholesale markets, the price of petrol fell 4.38p to 96.57p per litre but across the UK the average price at the pump dropped just 0.27p to 128.88p.
Diesel prices also fell, by a less significant 1p per litre, with just 0.38p of that saving being passed along to bring an average litre to 131.66p.
The RAC has now called on retailers to cut their forecourt prices to pass their savings on to customers.
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.”
The supermarket “big four” did reduce their prices slightly more than the average, with cuts of 0.55p on petrol and 0.6p on diesel bringing their prices to around 3.5p lower than the national average.
Mr Williams added: “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.
“By our calculations retailers ought to be charging around 126p for a litre of unleaded based on a wholesale price of 98p a litre, which many retailers will have bought at a couple of weeks ago, and then factoring in delivery, a reasonable margin of 5p a litre and VAT. As for the supermarkets they could easily be selling at around 122p.”
Regional data showed that drivers in the south-east paid most for both fuel types – 129.72ppl and 132.73ppl – while those in Northern Ireland enjoyed lower prices than the rest of the UK at 126.01ppl and 129.02ppl.
“If Northern Ireland can charge a fairer price why can’t retailers in the rest of the UK do it?” said Williams. “For this reason we strongly urge all retailers outside of Northern Ireland to cut their prices in the next week by at least 2p a litre on both petrol and diesel.
“There was a time when a 4.5p reduction in the wholesale price would have led the supermarkets to cut their prices significantly, but unfortunately those days seem to have passed.
“Perhaps they are hedging their bets thinking there could be a further drop in the value of sterling which will could cause wholesale prices to increase again.”