Drivers are paying £10 more to fill their car with petrol because of increases since the start of the year, according to the local consumer watchdog.
The Consumer Council called for greater transparency from the fuel industry and said buyers had endured unprecedented changes.
It now costs £54 to fill the average car with petrol.
"The fuel industry supplying our petrol and diesel needs to do more than simply tell consumers they are getting a good deal," Aodhan O'Donnell, head of transport at the Council, said.
"It must explain to consumers how the costs incurred at each stage of production and supply affects the final price paid at the pumps. Consumers do accept that the price of petrol and diesel will fluctuate but they must be provided with consistent information on what is driving the cost both upward and downward.
"This is a positive challenge for the fuel industry to demonstrate fairness to consumers in its pricing."
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