Drivers of diesel vehicles in the UK are paying up to 3ppl more than they should for their fuel, according to the AA.

In its latest Fuel Price Report it says the average gap between petrol and diesel prices at the pump is 5.23ppl, but the gap at wholesale level averaged just 0.8ppl over the past month.

Pump prices for mid June average 130.47ppl for petrol and 135.70ppl for diesel. A month ago, the fuels averaged 129.92ppl for petrol and 136.26ppl for diesel.

AA analysis of the wholesale prices versus pump prices suggests that part of the differential is due to retailers taking a smaller margin on petrol – about 1ppl less than a year ago – but it says that even when this is taken into account the price of diesel prices is about 3ppl higher than it should be.

AA president Edmund King said: “The pump price battleground is usually centred on petrol, the UK’s headline car fuel. However, the pumped-up price of diesel so far this summer is hitting 35% of UK car owners and is inexcusable. Neighbouring European countries have passed on the benefit of lower diesel wholesale costs to their drivers while the UK’s fuel industry has chosen to siphon off the savings.

“It has long been known that, for short periods, diesel margins can be a penny or so higher than petrol. Yet greater local price competition, more miles to the gallon and a longer time between fill-ups has meant that the diesel mark-up has gone largely unnoticed. This summer the gap is too big, gone on for too long and is therefore even more unfair. Additionally, with businesses passing the higher diesel costs for transport and deliveries direct to their customers, the inflated pump price is hurting non-drivers as well.

“Plummeting sales this spring have inspired retailers, particularly supermarkets, to cut their margins on petrol, and this is very welcome. But this shouldn’t be done at the expense of diesel drivers.”

Looking at overall fuel prices the report says the crisis in Iraq has helped to lift the price of oil from around $109 a barrel at the beginning of June to above $113 at the beginning of this week. However, much of the potential to push up wholesale prices was offset by a stronger pound breaching the 52-week high against the dollar, after the Bank of England’s governor hinted at an interest rate rise.