Supermarkets and other fuel retailers were warned on Monday they will be named and shamed if they rip off motorists by making excessive profits from petrol and diesel sales.
Energy Security Secretary Claire Coutinho issued the warning amid reports that garages are raking in profits at the expense of drivers.
She tweeted: "Drivers should get a fair price at the pump.
"I’ve written to fuel retailers to make it clear they must pass on savings. I will not hesitate to call out retailers who rip off the public."
She stressed that the Competition and Markets Authority would shortly be publishing a report on road fuels."The work is crucial to ensure that the road fuels market remains competitive and consumers interests are protected," she wrote in a letter to the bosses of retail firms.
Fuel prices have recently been pushed up by the escalating crisis in the Middle East.
But major fuel retailers are being urged by motoring experts to cut petrol prices by 5p per litre because they have allegedly increased their profit margins.
The RAC, which issued the plea, accused fuel-selling supermarkets of hiking this gap.
Its analysis found their margins on petrol are around 14p per litre, double the long-term average of 7p.
Latest figures show average petrol prices in the UK are 155.3p per litre.
Petrol prices should be lowered by 5p per litre while diesel should be cut by 4p per litre, according to the RAC.
The 5p per litre cut in fuel duty introduced by the Government in March 2022 "only appears to be helping retailers who have chosen to up their margins", the company said.
An investigation by the CMA found that supermarket fuel retailers overcharged drivers by 6p per litre in 2022, costing them a total of around £900 million.
The CMA recommended retailers provide live pump price information and a price monitoring body is created.
The Government has pledged to legislate for both those measures.
RAC fuel spokesman Simon Williams said: "Our analysis sadly shows that despite the Competition and Markets Authority's investigation confirming drivers were being ripped off at the pumps - something we have been saying for years - and the Government acting on the findings, nothing has changed.
"Drivers are still losing out massively when wholesale prices come down.
"Drivers and, indeed, the Treasury, should be furious that the 5p per litre duty cut, which has been in place since the end of March 2022, is not being passed on at forecourts."
