Drivers of petrol vehicles continue to get a "raw deal" despite a record monthly drop in pump prices, according to a new analysis by the RAC.
The British automotive services company said on Monday that the new prices "remain a long way off" what it believes to be fair.
It means drivers were spending around £6.77 less to fill a 55-litre petrol car than they did a month ago.
However, the RAC said the reduction didn't fully reflect the drop in wholesale prices.
"By the end of August wholesale prices were lower than they were at the start of the month, so even factoring in buying cycles there is a very strong case for the biggest sellers of fuel to cut their forecourt petrol prices further," RAC spokesman Rod Dennis said in a statement.
While "allowing for a generous 10 [pence] a litre margin," petrol should be sold for around 161 pence per liter at the pumps, he said, adding that there's a real postcode lottery in petrol prices, meaning drivers have to shop around for better prices.
According to the RAC, petrol prices varied in different regions of the UK on Aug. 31, ranging from 167.22 pence per litre in Northern Ireland to 170.89 pence per litre in southeast England.
The average diesel price per litre dropped by 8.35 pence in August, from 192.06 pence at the beginning of the month to 183.71 at the end. The prices range from 180.58 in Northern Ireland to 184.61 in southeast England.
The RAC said it believes this is "a fairer reflection of wholesale prices" compared to petrol.
Taxes, including fuel duty and VAT, made up almost 48 percent of the average petrol price on Aug. 31 and 49 percent of the average diesel price.
Dennis called on government ministers to offer a "deeper cut" in fuel duty and consider "much more generous packages of help being offered to those in other countries across Europe.”