Diesel sells for about 17p a liter more than petrol on average, although wholesale costs have fallen to similar levels, a carmaker said.
Average diesel prices are £1.64 a liter compared to £1.47 a liter for petrol, while both wholesale are around £1.15, the RAC said.
The difference was “scandalous” and the wholesale price reduction was not passed on to customers.
Retailers said they “understood the cost pressures” drivers were facing.
Supermarkets and private retailers buy fuel on the wholesale market to sell to consumers.
The RAC, which tracks fuel prices and tracks campaigns, said wholesale prices for diesel had fallen and were now, on average, the same as petrol.
But Simon Williams, fuel spokesman for the Motoring Group, said there was “still over 17p difference at the pump”, which he described as “absolutely shocking”.
Mr Williams said given the amount wholesale prices have fallen, petrol stations should already have cut diesel pump costs to around £1.52 and a further cut to £1.47 in the coming weeks should take hold.
When prices change in the wholesale market, it can take time for the changes to take hold at the dispensers, as smaller sellers often replenish.
But Mr Williams said larger supermarkets, which dominate sales, have had “plenty of time” to pass lower prices on to customers.
Supermarkets buy fuel more often than independent sellers.
“She [supermarkets] absolutely resolutely refuse to lower their prices significantly, which is scandalous in a cost-of-living crisis,” he said.
“For retailers to average nearly 20p a liter margin in March compared to the long-term average of 7p is devastating for any driver and any business that relies on diesel.”
However, the British Retail Consortium, which represents supermarkets, said: “Retailers understand the cost pressures faced by drivers and will do everything possible to offer the best value for money across all service stations.”
The trade association didn’t comment directly on the price differentials, but said that as prices at the pump tend to lag wholesale prices, recent falls in wholesale diesel prices were still filtering through to consumers.
Fuel costs rose sharply after the Russian invasion of Ukraine as global oil prices surged above $130 a barrel.
In the meantime, however, crude oil prices have returned to pre-war levels.
Nathan Piper, an oil and gas analyst, told the BBC that diesel prices tend to be higher because the UK has to import the fuel while it is self-sufficient in petrol production.
Before the war in Ukraine, Britain imported about 20% of its diesel from Russia.
Mr Piper said the disruption in ties with the country meant prices rose as global demand increased.
But there has been criticism from car associations like the RAC that while petrol dealers have been quick to raise prices, they have been slower to lower them as costs have fallen.
A competition investigation is underway to examine whether retailers have made greater profits from so-called ‘rocket and feather’ pricing, where fuel prices rise while wholesale costs rise but then fall more slowly than costs fall.
The Competition and Markets Authority (CMA) regulator in its latest update said it saw some evidence of this in 2022, particularly for diesel prices.
Add Comment