The Consumers' Association (CA) has accused Apple of taking too big a bite out of UK music lovers' money.
It has asked the Office of Fair (OFT) to investigate the potential breach of competition law.
Under European law UK consumers are supposed to enjoy the same benefits of the single market as other citizens of EU member states.
But the CA said the service is more expensive for UK consumers, who are charged 79p - around 120 euro cents - to download one track, whereas in both France and Germany the cost is just 99 euro cents.
The watchdog is also concerned that Apple prevents UK consumers from taking advantage of the cheaper download service offered to French and German customers because of the terms and conditions UK customers have to sign.
To take advantage of the cheaper service, UK consumers need a registered address and payment mechanisms in France or Germany, which the CA claimed frustrates consumer benefits possible under the single market.
"Consumers' Association has submitted a letter of complaint to the OFT urging them to investigate what appears to be anti-competitive and discriminatory behaviour by iTunes against UK consumers," said Phil Evans of the CA in a statement.
"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. If the OFT agrees it will be another example of the rip-off culture that the British public are often victims of."
When asked by the CA about the different pricing Apple said: "The underlying economic model in each country has an impact on how we price our track downloads.
"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."
Apple told vnunet.com that it had nothing further to add to this statement.
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