The RAC’s Fuel Watch report for June shows that diesel wholesale prices are 1p to 3p a litre lower than petrol yet the average price of a litre of diesel is 120p, compared to 117p for petrol.

The RAC said that the vast majority of retailers continue to keep a significant gap between the two fuels with diesel often 5p a litre more expensive. It added that the latter group may be operating on wafer thin margins on petrol in order to remain competitive and trading this off against bigger margins on diesel in order to balance the books.

RAC fuel spokesman Simon Williams said: “Not only are diesel drivers now being demonised due to the increasing concerns over harmful nitrogen dioxide and particulate emissions, they are consistently having to pay a premium for their fuel. And, all this comes after years in which the taxation system has encouraged motorists to buy low carbon dioxide emitting vehicles. This has led to a big take-up of small fuel-efficient diesel vehicles by motorists believing their choice of vehicle was good for the environment as well as their pocket.

“While retailers are obviously free to choose how much they charge for petrol and diesel, we believe that motorists deserve to be treated fairly and that means forecourt prices that reflect the wholesale market.” 

The RAC’s Fuel Watch report shows that the price of diesel should drop by around 5p a litre in the next two weeks based on lower wholesale prices, although the motoring organisation has seen this throughout June with little to no forecourt price change so therefore has little hope of this saving being passed on. 

Simon Williams added: “Essentially, what is required is a fundamental re-balance of pricing in the retail fuel market. We need greater transparency and a fairer pricing model for both petrol and diesel. We realise that with more and more forecourts shutting up shop every month that fuel retailing may not be as profitable as it once was, but there seems to be a clear intention to make more money from a higher diesel price while at the same time being seen to maintain a lower petrol price.”