Average prices have gone down from 138.95p a litre in mid October to 135.08p, with diesel down from 143.74p to 141.89p.
But the fall in wholesale petrol prices across Europe should have knocked 10p to 11p a litre off UK prices, the AA said.
The AA added that despite the threat of an Office of Fair Trading investigation of the market, "conditions that led to drivers and businesses being short-changed at the pump in the spring have happened again".
The AA said UK drivers were also suffering again from price postcode lottery where motorists in one area can be charged up to 5p a litre more than drivers a few miles away.
On average, the cheapest petrol at the moment is in Yorkshire and Humberside (134.3p a litre) and the most expensive is in south-east England at 135.7p.
Yorkshire and Humberside also has the cheapest diesel (141.0p) with Northern Ireland the most expensive (142.6p).
Motorists received another blow this week when Labour's Commons motion to have the planned January 3p-a-litre fuel duty rise deferred was defeated.