British motorists have been paying over the odds for fuel, as calls mount for the Government to investigate “profiteering” petrol stations.

Petrol costs soared in recent months after wholesale prices skyrocketed. But while the wholesale price has now dropped, retailers have failed to pass on the difference to customers.

Retailers took an average profit margin of 16p a litre last month, compared to the long-term margin of 6p a litre. Motoring group the RAC estimated motorists paid an extra £5m a day in December as a result.

Retailers in other countries have passed on the drop in wholesale costs. Forecourts in Germany and Belgium currently charge around 136p a litre, the price British motorists would pay if profit margins were at normal levels.

While petrol prices in Italy, Greece and Sweden are broadly similar to Britain, most prices across the continent are much lower. The average cost per litre across the European Union’s 27 member states is 128p per litre, about 24p cheaper than fuel in Britain.

Filling up a typical 55-litre family car at this price abroad would be roughly £10 cheaper than doing so in Britain. 

The RAC’s Simon Williams said: “Drivers have been taken advantage of by retailers. Their resistance to cutting prices and to only pass on a fraction of the savings from lower wholesale costs is nothing short of scandalous.”

Mr Williams said every extra penny petrol stations took as margin led to drivers paying even more in VAT, which is levied on petrol and diesel at 20pc.

“This means the Treasury’s coffers have been substantially boosted on the back of the retailers’ action,” he said. “We urge ministers to push retailers into doing the right thing.”

Campaigners have called on the Competitions and Markets Authority, the pricing watchdog, to investigate the fuel supply chain.

Howard Cox, of Fair Fuel UK, a campaign group, said: “The Government’s management of this opportunistic profiteering beggars belief. 

“These greedy rip off prices are crippling families and businesses and accelerating the rise in inflation. 

“Boris Johnson should get rid of his biased, ill-informed, green, metropolitan advisors and restore confidence in this Tory administration by listening to Britain’s 37 million drivers.”

Gordon Balmer, of the Petrol Retailers Association, which represents around two thirds of forecourts, said the cost of running petrol stations had climbed over the year. 

He said that electricity prices had climbed 19pc, with wage inflation and increased National Insurance also adding to cost pressures. 

Mr Balmer said: “When customer volumes fall and operating costs rise, it makes sense for fuel retailers to raise margins if they are to remain in business.”

About 58p per litre of petrol is made up of fuel duty, which has been frozen in Britain since 2010. Along with VAT, this means that two-thirds of the cost of each litre of fuel goes straight to the Government.

Last October the Government scrapped a further planned rise to fuel duty that it claimed would have cost drivers an extra £15 every time they filled up.