Drivers are still paying 10p more for petrol than they should be, as major retailers fail to pass on the 5p fuel duty cut.

Drivers are being overcharged £5 for an average tank of petrol and £2.50 for diesel due to retailers not passing on the 5ppl duty cut, according to the RAC

The average price of petrol fell by 7.5p a litre in November to 146.95p – but the RAC warns that drivers are “far from getting a fair price on the forecourt despite recent government intervention”.

Diesel came down by almost 7p to 154.40p last month, but is also being overcharged by 5p a litre, due to retailers not passing falls in wholesale costs to drivers, according to the RAC.

It believes petrol should be sold for an average of 137p and diesel for 150p, based on retailers taking a fairer margin.

Average retailer margin on petrol is now 17p a litre and 13p for diesel, according to the RAC analysis – this compares to long-term averages of 7p for petrol and 8p for diesel.

It means drivers are currently paying around £5 more than they should be to fill up an average 55-litre family car (£80.62 v £75.35). For diesel, the figure is around £2.50 (£84.92 v £82.50).

And the RAC says drivers have lost out to the tune of a staggering £184m over the last two months as a result of retailers not passing on the 5p duty cut implemented in March 2022. Instead, it says major retailers are gaining from this.

Membership-only retailer Costco is bucking the trend. It’s currently selling unleaded for an average of 133.7p and diesel for 144p – 14p and 11p less than the UK average respectively. In Northern Ireland, unleaded is being sold for an average of 141.4p and diesel for 149.5p – 5.5p and 5p less than the UK average.

Independently run forecourt Grindley Brook, based in Whitchurch, Shropshire, is only charging 131.9p for petrol – matching Costco’s cheapest price, and 15p cheaper than the UK average – and 143.9p for diesel, 10.5p lower than the UK average.

By comparison the average price of unleaded at the big four supermarkets is 143.37p and 151.48p for diesel.

RAC fuel spokesman Simon Williams warned that major fuel retailers “don’t seem to have heeded the warnings levelled at them by Energy Secretary Claire Coutinho at the end of October saying she wouldn’t hesitate to call out those that rip off the public”.

He added: “While the Energy Secretary’s action may have encouraged retailers to begin reducing their prices, it’s undoubtedly a case of far too little, far too late. The wholesale market data the RAC analyses shows the true picture and unfortunately, for the Government and drivers, it shows the 5p-a-litre duty cut is not getting to drivers at all, and prices aren’t falling nearly fast enough yet again.

“We’ve contacted her department to explain what’s really going on with a view to prompting greater and more effective intervention. If a price monitoring body had already been set up by now – as recommended by the Competition and Markets Authority and accepted by the Government – then this might have been prevented and people might finally be getting a fairer deal at the pumps.”

Williams added: “We reiterate our call to the biggest retailers to significantly cut their prices to mirror what’s happening with greatly reduced wholesale costs.”

Drivers can also use the free myRAC app to cut fuel costs. It features a fuel finder feature able to save up to 6p a litre, according to the RAC.