The EU's Article 29 Working Party is made up of the 28 authorities responsible for enforcing data protection law. It wrote to Microsoft last year expressing concerns about the default installation settings of Windows 10 and users' apparent lack of control over the company's processing of their data.

The group wanted more explanation of Microsoft's processing of personal data for various purposes, including advertising.

The Group said that Vole was willing to co-operate but the working party remains concerned about the level of protection of users’ personal data.

Several national authorities have already begun enquiries into Windows 10, including France which in July ordered Microsoft to stop collecting excessive user data.

The EU privacy group said that despite a new installation screen presenting users with five options to limit or switch off Microsoft's processing of their data, it was not clear to what extent users would be informed about the specific data being collected.

Microsoft uses data collected through Windows 10 for different purposes, including advertising.

"Microsoft should clearly explain what kinds of personal data are processed for what purposes. Without such information, consent cannot be informed, and therefore, not valid," the group said.