The study by FairFuelUK found drivers have been paying around 4p to 5p more than they should have been in the last three months as oil companies fail to cut petrol prices in line with falling wholesale costs.

In the 12 weeks between 28 March and 15 June, wholesale prices to forecourt retailers increased by 5.4p for diesel and 4.5p for petrol, but pump prices rocketed by 75% – 9.5p – for diesel and 108% – 9.4p – for petrol, according to FairFuelUK’s analysis.

The campaign group said the fuel supply chain business has made £500m of extra profit in the last three months.

It said: “In the last few months the fuel supply chain has opportunistically hit UK drivers with greedy pricing strategies, using the Iran-Trump spat, the weaker pound and OPEC production levels posturing.

“These multiple influential factors on the price of oil have been exploited to dishonestly drive up profits at the pumps. In addition, inflation would have been lower if the correct and honest pump prices had been in place.”

FairFuelUK is calling on the government to monitor fuel price charges, including the big variations across the UK.

In a 30-mile radius of Bristol, petrol and diesel prices vary from supermarkets to independent forecourts by around 30p a litre.

Howard Cox, FairFuelUK Campaign founder, said: “In Germany and France, pump prices can fluctuate daily, even hourly. The cost of filling up in these countries accurately reflects oil and wholesale prices. Here in the UK motorists and businesses are exploited ruthlessly by greedy speculators and the fuel supply chain. The government must protect consumers and the economy from this recurring disingenuous manipulation by creating PumpWatch.”