The price premium being charged for diesel over petrol at UK filling stations is well in excess of a fair amount based on wholesale prices, according to the RAC.

The motoring organisation said its most recent data showed that diesel was being sold for an average of 168p per litre, compared with 148p for petrol – a 20p price difference, despite the wholesale price premium for diesel over petrol being less than 6p per litre, at 121.06p for diesel versus 115.48p for petrol.

The RAC said its analysis showed retailers were taking more than double the margin on every litre of diesel they sold compared with petrol – in effect, subsiding petrol prices by charging more for diesel.

It said that if diesel was being sold at a fairer rate, prices would be no higher than around 155p per litre.

RAC spokesman Simon Williams said: “While our data shows petrol is generally being sold at a fair price at forecourts at the moment, drivers of the country’s 12m diesel cars – as well as almost every white van driver – have every right to feel hard done by as they’re paying a huge premium for the fuel which in no way reflects its lower wholesale cost.

“For nearly a month, the gap between wholesale petrol and diesel prices has been less than 10p a litre and in recent days it has reduced to just 3.5p, yet average diesel prices at the pumps remain stubbornly high having fallen by only 2p since the start of February. 

“The fact membership-only retailer Costco has been able to cut the average price of a litre of diesel by a massive 4p this week shows what’s possible, but we badly need other fuel retailers to treat drivers of diesel vehicles fairly.

“Even though the price of diesel is not being cut as quickly as it should be, the gap between the average prices of petrol and diesel has dropped to under 20p (19.99p) for the first time since 10 October 2022. If retailers now do the right thing this should reduce significantly, saving drivers who rely on diesel a lot of money every time they fill up.”