European privacy activists have filed a complaint against Apple over software that tracks the behaviour of iPhone users.
The Vienna-based non profit group noyb which stands for "none of your business" says it has asked data protection authorities in Germany and Spain to examine the legality of Apple's tracking codes.
The codes, known as Identifier for Advertisers (IDFA), are similar to the cookies that websites use to store information on a user's behaviour.
But the non-profit group says that Apple's iOS operating system creates unique codes for each iPhone that allow the company and other third parties to "identify users across applications and even connect online and mobile behaviour."
The group argues that this amounts to tracking without users' knowledge or consent, and violates the European Union's electronic privacy rules.
The privacy group said it is also currently reviewing a similar system used by Google.
"Tracking is only allowed if users explicitly consent to it,'' said Stefano Rossetti, a lawyer for noyb in a statement.
"While Apple introduced functions in their browser to block cookies, it places similar codes in its phones, without any consent by the user. This is a clear breach of EU privacy laws."
"Smartphones are the most intimate device for most people and they must be tracker-free by default," says Rossetti.
Apple has dismissed the claims, made by the group, saying they were "factually inaccurate".
"We look forward to making that clear to privacy regulators should they examine the complaint," the company said.
"Apple does not access or use the IDFA on a user's device for any purpose. Our aim is always to protect the privacy of our users".
The tech giant has also stated that the latest version of its software gives users greater control over whether apps can track them, including whether their information can be linked with data from third parties for the purpose of advertising, or sharing their information with data brokers.
"Our practices comply with European law," Apple said.
The non profit group has filed numerous cases against major tech companies, including one against Facebook that recently led the European Union's top court to strike down an agreement that allows companies to transfer data to the United States over snooping concerns.