nergy Secretary Grant Shapps has warned fuel retailers he will “call out any foot-dragging” over the sharing of pump price data.
He made the comment as drivers were hit by the largest weekly rise in petrol prices for more than a year.
The Competition and Markets Authority (CMA) is planning to launch an interim voluntary system for retailers to publish fuel prices by the end of the month.
Mr Shapps claimed households are “not getting a fair deal on fuel and are being overcharged”.
In a letter to CMA chief executive Sarah Cardell, he wrote: “I want to reiterate the Government’s strong support for the CMA’s temporary scheme for major retailers to make their daily prices available in a common, machine-readable format by the end of August.
“I strongly expect retailers to co-operate with the CMA to develop the voluntary scheme to this timeline and I will not hesitate to call out any foot-dragging.
“Please do keep my officials abreast of participation in the voluntary scheme so we can act if necessary.”
Mr Shapps added that the Government “remains committed” to developing a mandatory open data scheme for fuel retailers “as soon as possible”.
Figures published by the Department for Energy Security and Net Zero show UK forecourts charged an average of 146.2p per litre for petrol and 148.2p per litre for diesel on Monday.
Analysis by the PA news agency found this represents the largest weekly increase in petrol prices since June last year at 2.1p per litre.
There was a largely uninterrupted fall in average petrol prices from late October 2022 until late June, but pump prices have now risen for three consecutive weeks.
AA pump price spokesman Luke Bosdet said: “The summer of cheaper petrol and diesel has fizzled out as oil producers cut production to force up the cost of oil and therefore increase road fuel prices.
“Drivers have complained about some very rapid rises at the pump – sometimes 2p or 3p a litre in one go.”
“This won’t help the cost-of-living crisis or inflation but, hopefully, more pump price transparency will pressure retailers to be more responsive when costs come back down again.”
Steve Gooding, director of the RAC Foundation, said: “High street retailers might be discounting their prices to lure us back to their shops, but there is no such luck at our service stations as fuel prices rocket just as many families are filling up for their summer holiday getaways.
“We can only hope that fuel companies are still feeling the eyes of ministers and the CMA on them as they calculate how much they really need to charge to cover their costs.”