Retail fuel margins are now 19 pence a litre, Mr Williams said, 12 pence above the long-term average.
‘Petrol really should be on sale for 153p a liter and diesel 175p,’ he said.
Mr Williams said independent retailers, who have traditionally been much more expensive than their supermarket competitors, now often sell at lower prices.
Larger retailers tend to buy their gasoline further in advance, which means wholesale price changes are slightly slower to trickle down to consumers, according to an industry source.
Andrew Opie of the British Retail Consortium said: “Retailers understand the cost pressures motorists face and will do all they can to deliver the best value on their forecourts, passing on cost reductions as they go. as they feed into the supply chain.
An Asda spokesperson said: ‘Asda has always offered motorists the best value at the pump. Since the beginning of July, our prices have fallen by 25 pence per liter of petrol and 18 pence per liter of diesel. In addition, current prices are 2 pence per liter lower than the UK average for petrol and 3 ppl for diesel. »
Tesco, Sainsbury’s and Morrisons have been contacted for comment.
Earlier this year, former Prime Minister Boris Johnson declared war on petrol stations that fail to pass on the Government’s fuel tax cut, pledging to name and shame those who refuse to lower their price.
Mr Johnson said he was furious that the 5p-a-litre fuel duty cut announced in March had not passed through to prices at the pump, prompting an investigation by the competition regulator.