Average petrol prices have fallen to their lowest level for nine months but there is a clear north-south divide in how much drivers are paying, the AA has said.
UK petrol pump prices now average 132.54p a litre - a level last seen in March and down 1.16p on a month ago.
But across London and south-east England, the average price is 133.55p a litre compared with 131.63p across northern England.
And diesel, nationwide, now averages 141.15p a litre - up from the mid-November figure of 140.95p.
The AA said that for the year in total, petrol has averaged 133.83p a litre, while the pump price of diesel has averaged 139.17p.
This compares with last year's 117.36p a litre average for petrol and 119.75p for diesel.
AA president Edmund King said: "As more severe winter conditions push up fuel consumption and families contemplate the cost of Christmas travel, it will anger many that pump prices remain artificially high in so many places.
"This is simply because there isn't the transparency in the fuel market to indicate where prices should be.
"Only when such glaring regional disparities as we've seen this month emerge or prices between neighbouring towns vary by as much as 4p a litre do motorists know that something is wrong."
He went on: "If it is a case that some of the cash consumers save at the supermarket checkout is clawed back at the pump, it is a risky strategy.
"AA research shows that 28% of its members budget a set amount on fuel, that rising to 40% among less well-off drivers.
"Getting to and from a superstore at the end of the week can easily consume a litre of fuel and that may be enough to make some customers shop closer to home.
"We are also seeing a growing number of independent retailers taking the opportunity to undercut supermarket rivals by as much as 2p a litre. Drivers just wish there were more."
Mr King continued: "Although falling oil prices have brought prices back to where they were in the spring, the relief isn't that great for rural and lower-income drivers.
"For many, this year has been like 12 rounds in the ring with a heavyweight boxer.
"Yes, the tempo of the pump price punches may have lessened, but drivers are still being pummelled. Some have been knocked out for good."