The dip in the price of petrol at the pumps has failed to match the fall in wholesale prices, the AA has revealed.
In the past week, average UK petrol prices have fallen less than 1p a litre despite falls in wholesale prices equivalent to at least 3p a litre, the motoring giant says.
The AA said last week that as supermarkets were cutting prices by around 2p a litre they should actually fall by 4p a litre to reflect the drop in costs.
- Petrol prices down by 1p/litre
- But wholesale prices fallen by 3p/litre
- Prices up on last year
Petrol at the pumps is now averaging 135.71p a litre, with diesel at 139.89p a litre.
The mid-August figures compare with 135.62p a litre for petrol and 139.68p for diesel in mid July.
Prices up on last year
Compared with a year ago, petrol is 19.22p a litre more expensive, while diesel costs 20.91p more.
Filling a typical 50-litre petrol tank now costs £9.61 more than a year ago, adding £40.81 to the monthly petrol spend of a two-car family.
Currently, Northern Ireland is the most expensive region for petrol (136.7p a litre) while Yorkshire and Humberside is the cheapest part of the UK (134.9p), the AA adds.
Northern Ireland is also most expensive for diesel (140.8p a litre), nearly 2p a litre more expensive than the cheapest region - Yorkshire and Humberside (139.0p).
AA public affairs head Paul Watters says: "Supermarkets announced that they would be cutting pump prices this week and, hopefully, the drop in wholesale costs will be more properly reflected at the pumps.
"However, there is clearly a need for price transparency covering oil, wholesale and retail markets, taking into account the exchange rate."