The AA says drivers are not seeing prices fall across the country
Several leading retailers are cutting the price of petrol and diesel, following recent falls in oil prices.
Morrisons is offering drivers fuel that is 2 pence cheaper on average from Monday while Asda has also cut costs.
Meanwhile Tesco said it will match the lowest petrol price locally at its forecourts and Sainsbury's had already announced it was trimming prices.
But motoring group the AA said that while the price cuts were welcome, they were not being seen across the country
"Cheapest prices in many southern towns are still two to three pence per litre above what drivers are paying in areas where competitive supermarkets are engaged in a dogfight," said Paul Watters, the head of public affairs for the AA.
"Price cuts have to be welcomed - whoever makes them," he added.
"But we don't see much fanfare from the supermarkets when they are putting prices up, which makes it hard to identify who is leading the way when there are price rises."
Morrisons said unleaded petrol will drop to 109.9p per litre while diesel is 121.2p.
Asda will cut prices to 109.9p per litre for unleaded petrol and 121.9p for diesel, effective from Tuesday.
Since peaking in July at $147.27 a barrel, oil prices have fallen nearly $30 a barrel on the expectation that lower economic growth would prompt lower demand.
Phil Maud, petrol director at Morrisons, said the move showed it was "committed to delivering real value for all our customers - whether they're filling up at our forecourts or shopping in our stores."
Since the all-time high of 119.7p a litre for petrol and 133.25p for diesel, the wholesale price for petrol coming into the UK has fallen 18% and 22% for diesel, he added.
"This has yet to be reflected in average UK prices."