Despite the average price of petrol and diesel falling by 6p a litre in November, data from RAC Fuel Watch shows that the reductions on the country’s forecourts should have been at least twice that.
Unleaded came down from 165.96p to 159.88p while diesel dropped from 190.31p to 183.87p.
The reason the RAC believes drivers have lost out is due to the wholesale price of petrol plummeting by 11p in November from 122.63p to 111.53p on top of significant reductions in late October.
Diesel decreased by even more last month, coming down 15p from 143p to 128p.
Taking an average of wholesale prices for the last week of November (21-25), the RAC believes petrol should really be at an average of 146p and diesel to 169p – 14p and 15p lower than the current averages.
It means retailers are now collectively enjoying margins of more than 20p a litre, the breakdown firm says.
A litre of unleaded bought at a supermarket costs 158.31p – down 6p in the month – but now only 1.6p lower than the UK average.
Supermarket diesel at the end of November was down 3.7p to 182.74p, only a penny below the average price across the country.
RAC fuel spokesman Simon Williams said: “It’s bordering on a scandal that drivers are being overcharged so much because the big four supermarkets, which dominate UK fuel retailing, are flatly refusing to reduce their prices by bigger amounts.
“Their prices are dropping like a feather when they should be falling like a stone.
“In 10 years of closely monitoring fuel prices we have never seen major retailer margins this high for this long.
“It used to be the case before the pandemic that we’d see wholesale prices drop by 4p a litre and then the supermarkets would be vying with one another to announce a price cut to drive customers into their stores.
“We saw some similar fuel pricing behaviour from the big chains last Christmas but despite this, we believe this is probably the worst example of ‘rocket and feather’ pricing we have ever seen.
“We hope the Competition and Markets Authority, which is currently investigating UK fuel retailing, is paying close attention.
“We would also remind the supermarkets that the Government’s 5p-a-litre duty cut is still in place and is intended to ease the burden on drivers.”