Petrol car drivers in the UK were overcharged by £5m every day in December, paying £156m more than they should have across the month.

RAC data reveals the price of unleaded should have come down by 12p if retailers had played fair when wholesale market prices fell

While average unleaded prices fell by 2p a litre last month, bringing them down to 145.48p, RAC data reveals the price of unleaded should have come down by 12p if retailers had played fair when wholesale market prices fell.

And despite a drop of just under 2p a litre to 148.92p, diesel was also overpriced by nearly 7p a litre.

RAC fuel spokesman Simon Williams said retailers’ resistance to cutting prices was “nothing short of scandalous”.

“In the past when wholesale prices have dropped retailers have always done the right thing – eventually – and reduced their pump prices. This time they’ve stood strong, taking advantage of all the media talk about ‘higher energy prices’ and banked on the oil price rising again and catching up with their artificially inflated prices, which it has now done.

“The trouble is every extra penny they take as margin leads to drivers paying even more as VAT gets added on top at the end of the forecourt transaction. This means the Treasury’s coffers have been substantially boosted on the back of the retailers’ action. We urge ministers to push retailers into doing the right thing for consumers.”

Williams added: “The only benefit of the current high fuel prices is the extra incentive for drivers to go electric as those driving 9,000 miles a year could save around £1,500.”

Asda had the cheapest petrol at the end of the year, according to RAC Fuel Watch data, with a litre costing an average of 141.81p at their stores, with Sainsbury’s not far behind at 142.57p. Asda also sold the lowest priced diesel at 144.9p a litre ahead of Tesco on 145.8p.

The average price of motorway unleaded at the close of December was 160.55p while diesel was higher still at 163.43p.