The price of diesel at UK pumps fell by nearly 4p a litre in April but is still at least 16p over what it should be, according to RAC analysis.

Diesel drivers are paying 16p a litre more than they should, according to RAC analysis

Its latest Fuel Watch data reveals that a litre of diesel closed the month at an average of 159.43p across UK forecourts, while petrol was unchanged at 146.5p.

It’s the sixth month that the average pump price of diesel has fallen but drivers are still paying more than they should as the wholesale price was lower than petrol for all of April.

A litre of wholesale diesel cost 104.88p on 28 April – down 9p in the month – whereas unleaded was 111.25p (down 6p in April).

However, apart from in Northern Ireland where diesel averages 147.47p, diesel in the rest of the UK is still 13p more expensive on the forecourt.

The RAC believes drivers should really be paying around 143p at the very most for a litre of diesel – which would slash around £9 off the current average cost of £87.69 for filling a 55-litre family car. The petrol equivalent is £80.60.

The data also shows that the average price of unleaded at supermarkets stood at 142.99p – 3.5p cheaper than the UK average – at the end of April while diesel was 2.75p cheaper than the average at 156.68p – down 3p since the start of the month.

RAC fuel spokesman Simon Williams has urged action on fuel prices as he warns that diesel drivers across the UK mainland continue to lose out badly at the pumps.

“Our data shows that the average retailer margin on a litre of diesel is a shocking 22p a litre compared to petrol which is around 8p. The long-term averages for both fuels is 7p which means retailers are making three times what they have in the past for diesel. This is hard for them to justify and equally hard for diesel drivers to swallow.

“Action at a government level is badly needed to stop drivers being ripped off any longer. While we’re not in favour of prices being capped – as we feel this could lead to smaller retailers in rural areas not being able to compete and going out of business to the detriment of the communities they serve – we feel there should be an obligation on the biggest retailers to charge fairer prices in relation to wholesale market movements.”

The RAC has called for an obligation on retailers to reflect wholesale price movements on their forecourts.

“Sadly, the only place this seems to happen is in Northern Ireland where a litre of diesel is, incredibly, being sold for 12p less than the UK-wide average,” Williams continued.

“We realise retailers need to make a profit but a margin of 22p on every litre of diesel can only be seen as outrageous and a slap in the face to those who depend on it, whether they’re consumers or businesses.”

Prices around the UK – in pence per litre