Fuel prices fell for the fifth straight month in March – but diesel drivers are still “blatantly being taken advantage of” by major fuel retailers not budging further on prices.

The average retailer margin on a litre of diesel at the end of March was 21p – three times the long-term average of 7

Last month saw another penny come off petrol and 4p off diesel, according to data from RAC Fuel Watch. It meant a litre of unleaded ended March at 146.5p (down from 147.56p) – a price last seen at the end of January 2022.

Meanwhile, diesel reduced to 162.94p (down from 167.06p) – its cheapest price since early March last year.

Since the start of November, the price of petrol has fallen nearly 20p from 166p  while diesel has dropped 27.5p from 190.5p, saving drivers some £11 and £15 a tank respectively.

But the RAC says diesel prices should have fallen much further at the pumps. Its wholesale price was very similar to petrol’s for most of March and became cheaper than petrol on the wholesale market on 23 March. It’s stayed that way since, finishing the month at 111.69p a litre compared to petrol at 115.81p.

RAC figures indicate that the average retailer margin on a litre of diesel at the end of March was 21p – three times the long-term average of 7p. In contrast, the margin on petrol was just 7p.

Analysis of fuel prices at the big four supermarkets show the average price of unleaded fell by 1.5p in March to 143.18p and diesel by 5.3p to 159.88p. Asda had the cheapest petrol at 142.69p (down 1p) and Tesco had the lowest priced diesel at 159.58p (down 6p).

By way of comparison, the RAC noted that a “small retailer at Whitchurch in Shropshire” is selling both petrol and diesel for just 142.9p a litre – and said there was surely no reason why the big four supermarkets can’t do this as well.

Member-only retailer Costco is still offering the most competitively priced fuel across the UK with petrol at 137.7p and diesel at 149.8p.

‘Galling’ comparison for diesel drivers

Average diesel prices in Northern Ireland provide a benchmark to how much diesel drivers “are being taken advantage”; the fuel is 10p cheaper at just 152.78p. Petrol is also 2.5p cheaper there – being sold for 143.97p at the end of the month.

RAC fuel spokesman Simon Williams said: “We hope the Competition and Markets Authority is paying close attention. The situation in Northern Ireland shows just how much diesel should really be being sold for. While there are several reasons why petrol and diesel are generally cheaper in Northern Ireland, it also can’t go unnoticed that the supermarkets aren’t as dominant in fuel retailing there as they are on the mainland.

“It simply cannot be fair on drivers that the retailer margin on diesel is currently three times more than the long-term average at 21p a litre. While retailers are free to charge what they like for fuel we feel there should be an obligation on the those which sell the most, and therefore buy most frequently, to closely reflect what’s happening on the wholesale market. If this had been the case then the forecourt price of diesel would have been down to around 152p a litre, even with an above-average margin.”