Labour has called on a watchdog to take a fresh look into whether motorists are being "fleeced" at the petrol pumps.
The Competition and Markets Authority (CMA) examined pricing on garage forecourts in 2013 but concluded no full investigation was required.
But shadow transport secretary Michael Dugher said recent cuts had still left the average litre of fuel more expensive than if a dramatic slump in the global oil market had been fully passed on.
He wants the CMA to use powers to launch an initial 'market study' to determine whether a full inquiry is merited.
"Hard-up families and hard-pressed businesses are fed up of feeling like they are being fleeced at the pumps," Mr Dugher said.
"We know that when oil prices go up, fuel prices go up. But when oil prices come down, as in recent months, it is not reflected in the prices people pay at the pumps.
"Britain's motorists are still paying an average of 118p a litre, even though global oil prices have fallen by more than 40% since July.
"Organisations have said that petrol should now be at least 7p a litre cheaper than it is."
Several supermarkets have announced cuts in prices in recent days.