According to RAC Fuel Watch, the price drop is due to the cost of oil dipping to $62 per barrel.

The average price of unleaded petrol dropped 3p a litre from 130.67p to 127.62p, while diesel reduced 4.61p from 135.51p to 130.90p – the ninth biggest monthly reduction in the price of a litre of diesel since 2000.

But despite the wholesale price of petrol in the first week of June reaching its lowest point since March (95.79p a litre), pump prices didn’t fall as far as they should have done. In stark contrast, when the wholesale price was a similar level in March unleaded was being sold at 123p a litre – more than 4p cheaper than the price during the last 10 days of June.

Simon Williams, RAC fuel spokesman, said: “Retailers were clearly banking on the oil price rebounding after its sudden drop which began at the end of May when a barrel was over $70. Inevitably this has meant bad news for drivers who have lost out with pump prices being 4p a litre more expensive than they should have been.

“Unfortunately, retailers’ hunch that oil would quickly increase again were right and now their prices are broadly where they should be based on the current wholesale price. They just happen to have made significant profits as a result of not passing on more of the savings to drivers than they did.”

The cost of filling up

The cost of filling up a 55-litre family car with unleaded petrol fell by £1.68p to £70.19 by the end of June. The saving on a tank of diesel was greater at £2.54, down to £72.

Looking at the average prices charged at the four big supermarkets there was a 6p a litre reduction in diesel, from 133p a litre down to 126.98p. With petrol, however, the cut was below the UK average at 2.67p, with a litre costing 124.08p by the end of June.

At the end of the month Asda had the lowest priced petrol at its sites at 123.25p a litre – only slightly ahead of Tesco with an average of 123.65p. Asda also had the cheapest diesel at 124.70p with its next nearest competitor more than 2p a litre more expensive.