Apple's iTunes music download service has been accused by the Consumers' Association of overcharging UK users.
Downloading one track costs UK customers 79p
The group accused the service of charging UK-based customers nearly 20% more than those with addresses and payment details in France or Germany.
The group has written to the Office of Fair Trading (OFT) asking it to investigate iTunes for possible breaches of EU competition rules.
Apple said its prices should be compared with other UK music downloads.
The Consumers' Association said that while iTunes charges UK based customers 79p to download one track, customers in France or Germany only have to pay 99 euro cents - the equivalent of 67p.
The association claimed that the iTunes service is set up in a way that prevents UK consumers from taking advantage of cheaper downloads.
UK consumers need to have a registered address and payment mechanism in France or Germany to access cheaper downloads, or face paying the higher price.
Consumers' Association spokesman Phil Evans said iTunes policy could be seen as anti-competitive and against EU rules.
"There appears to be considerable evidence that the iTunes set up is prejudiced against the UK public and distorts the very basis of the single market," he said.
"If the OFT agrees it will be another example of the rip-off culture that the British public are often victims of. "
But Apple defended their UK pricing policy.
"The underlying economic model in each country has an impact on how we price our track downloads," an Apple spokeswoman told BBC News ONline.
"That's not unusual - look at the price of CDs in the US versus the UK. We believe the real comparison to be made is with the price of other track downloads in the UK."