The Office of Fair Trading (OFT) is due to release a review into whether reductions in the price of crude oil are being passed on to motorists.
The OFT will then decide whether to launch a full investigation into fuel prices.
Edmund King, president of the AA said it was time the OFT investigated the fuel industry:
"The Office of Fair Trading decides soon whether to launch an investigation into fuel prices, hopefully tackling the fuel industry's treatment of drivers, consumers and businesses."
Brian Madderson, from the Petrol Retailers Association (PRA), called on the OFT to launch an investigation into the wholesale market rather than target petrol stations.
More top news
The Duke of Cambridge has condemned the "violent and apparently targeted murder" of the head of a wildlife conservation foundation.
Experts are warning that millions of middle-aged people are putting their health at risk due to a severe lack of exercise.
Teenagers across Wales, Northern Ireland and England are to get their results, with much of the focus on the effect of reforms in England.