A watchdog investigation on if supermarkets are overcharging customers for fuel and groceries has been launched. 

It comes as the Competition and Markets Authority (CMA) is looking into whether there is 'any failure in competition' forcing customers to be paying more. 

No specific supermarket chain has been named, as the CMA shared that there was no evidence aimed at one. 

They stated that concerns were raised when supermarket fuel prices became more expensive by 5p per litre in 2022 compared to pre-pandemic costs. 

CMA said that one reason for increased costs was Russia's invasion of Ukraine seeing people pay more at the pump. 

Alongside the cost of petrol, supermarkets have come under criticism as the CMA states: "‘Higher pump prices cannot be attributed solely to factors outside the control of the retailers."

The evidence provided by supermarkets for the investigation found that: "Whilst the level of engagement with the study has varied across supermarkets, we are not satisfied that they have all been sufficiently forthcoming with the evidence they have provided."

To help fix the issues, the CMA plans to conduct "formal interviews" with senior management at the supermarket brands. 

However, the CMA did also add that supermarkets are still the cheapest fuel suppliers but did add that "at least one" brand has "significantly increased" the cost. 

Speaking of the costs, Secretary of State for Energy Security and Net Zero, Grant Shapps said: "We won't stand for motorists being treated like cash cows and ripped off at the pumps.

"Fuel prices are falling so there is absolutely no excuse for retailers to not pass those savings on.

"Supermarket bosses must fully cooperate with the watchdog's investigation and if they refuse to play ball I won't hesitate to take action."