The Government is to take action to get petrol companies to pass on cuts in global oil prices to motorists at the pumps.
Transport Secretary Justine Greening has called on fuel retailers to set up their own code of practice so consumers can monitor daily petrol or diesel prices.
If the industry does not do it, then the Government plans to introduce legislation.
Motoring groups and fair fuel campaigners have long complained of the slowness of filling stations to lower pump prices if world prices fall.
Ms Greening told The Sun newspaper: "Petrol prices go up instantly when wholesale prices rise, but when wholesale prices fall, it can take weeks for them to come down again.
"It is indefensible that motorists should be ripped off. It's time the big companies started playing fair with the motorist, so I am giving them one last chance."
She went on: I want companies to come up with their own plan as soon as possible - and I'm talking days and weeks, not months.
"That way we can get prices down faster, rather than having to pass time-consuming legislation. But we will certainly do that if we have to."
AA president Edmund King said today: "Over the past seven years we have asked governments to act against the blurred world of UK pump prices, which every driver knows shoot up like a rocket and fall like a feather.
"MPs have joined the chorus of complaints against postcode lottery pricing where some towns charge up to 5p a litre more for their cheapest petrol compared to another town down the road. Yet nothing happened."
He went on: "At last, we have a Transport Secretary who is prepared to act to win a better deal on fuel prices for consumers.
"This month, the German government announced a move towards fuel price regulation. The Austrians have already implemented regulation and, even with a weaker euro, their pre-tax petrol prices remain cheaper than the UK's.
"The Danes already have a system of price reporting and transparency up and running. Clearly, patience is running out with record fuel prices across Europe and there is a will to act.
"The AA supports a move towards transparency on fuel prices. However, with record prices cutting sales by 5% last year and 76% of AA members cutting back on car use, other family spending or both, regulation has to remain an option."