Drivers paid nearly £1 billion more for fuel at supermarkets last year due to increased margins, an investigation has found.
Watchdog the Competition and Markets Authority (CMA) said average supermarket fuel margins rose by 6p per litre between 2019 and 2022.
That led to an estimated combined additional cost of “around £900 million” for customers of Asda, Tesco, Sainsbury’s and Morrisons, a report stated.
The inquiry also found that an increase in margins on diesel across all fuel retailers cost drivers an extra 13p per litre during the first five months of this year.
The CMA recommended that the Government introduces legislation requiring retailers to provide up-to-date pricing information available in an accessible format.
This would allow drivers to compare pump prices at different sites through apps or satnavs.
The watchdog also called for a new fuel price monitoring body to be created to hold the industry to account.
Supermarket giant Asda was fined £60,000 by the CMA for failing to provide relevant information in a timely manner.
CMA chief executive Sarah Cardell said: “Competition at the pump is not working as well as it should be and something needs to change swiftly to address this.
“Drivers buying fuel at supermarkets in 2022 have paid around 6p per litre more than they would have done otherwise due to the four major supermarkets increasing their margins.
“This will have had a greater impact on vulnerable people, particularly those in areas with less choice of fuel stations.
“We need to reignite competition among fuel retailers.”