Drivers are paying an extra £5 per tank of fuel due to the devaluation of the pound, according to a new analysis.
The association said the savings in pump prices from the lower cost of oil to what it was before Russia’s invasion of Ukraine was “severely undermined” by the weakness of the pound sterling.
The motoring organization has calculated that the UK front-court petrol would be “at least” 9p per liter if the pound had held its value in mid-February at $1.35.
The difference in pump prices adds around £4.95 to the cost of filling up a typical 55L family car.
Gasoline averaged 164.8p per liter at the start of the week, down from 173.5p in mid-August.
But the 8.7p drop is less dramatic than the 15p drop between mid-July and mid-August.
The average price of diesel fell 12.5 pence between mid-July and mid-August, before dropping another 3 pence to 181.3 pence at the start of the week.
AA fuel price spokesman Luke Bosdet said: “The impact of the exchange rate is often overlooked when drivers compare oil price movements to those at the pump.
“Right now, it’s critical. Oil and fuel in the commodity markets are traded in dollars, making a weaker pound very bad news for motorists.
“The price of oil has returned to the level it was at the beginning of the Ukrainian war, but the price of gasoline has reached 15 pence per liter.
“Two-thirds of this high cost is due to the weakness of the pound.”
Mr. Bosdet added that it is possible to buy gasoline about 10 pence a liter below average prices by finding a “competitive front yard” that sells fuel for as little as 155 pence a liter.
The US currency has been strong against the British pound for several months.
The latest decline comes as Chancellor Kwasi Koarting unveiled the biggest tax cuts in 50 years as part of a new economic agenda – a package that will be paid for by a massive jump in government borrowing.