The British government is facing calls for action as forecourt prices for petrol and diesel hit record highs at the weekend.
The average price of diesel in the UK rose to a record 182.59p a litre on Sunday and petrol prices increased to a record 172.73p a litre, according to the AA.
The cost of filling a family car with diesel has exceeded £100 for the first time.
Chancellor Rishi Sunak cut fuel duty by 5p a litre in March, but campaigners have accused retailers of increasing their margins rather than passing the reduction on to drivers.
The wholesale price of diesel is cheaper than petrol, but diesel is still more expensive at the pumps.
RAC analysis showed that retailer margins on diesel have grown to 11p a litre in recent weeks, exceeding the long-term average of 8p.
Motoring groups yesterday pointed out that diesel is used by the majority of van drivers and haulage companies, meaning that higher fuel costs will likely be passed on to consumers, further pushing up prices for goods in shops, the Daily Mail reported.
British drivers are paying more in fuel tax than they did 12 months ago, based on official figures from the Department for Business, Energy and Industrial Strategy (BEIS).
The government is benefitting from higher fuel prices as VAT is charged at 20% and the Liberal Democrats are calling for an emergency VAT cut to 17.5%.