The BBC has been threatened with a complaint to the European Commission (EC) over its contoversial use of Microsoft technology in its upcoming iPlayer.
Advocacy group the Open Source Consortium (OSC) has attacked the online video service as anti-competitive as it will only initially work on Windows-based computers.
Mark Taylor, the group's president, said the BBC had “a mandate to provide equal access to people irrespective of platform".
Set for launch next month, the iPlayer will use Microsoft's system to allow viewers to catch-up with shows up to 30 days after they are broadcast.
The OSC has previously complained to the DTI, BBC Trust and Ofcom about the service, although the media regulator has said the iPlayer would be "only one of many factors influencing the decision to purchase an operating system".
Nevertheless, Taylor said the group’s next step would be to submit a formal complaint to the EC:
"We're preparing the full details at the moment and we will be sending a formal letter within the next week.”
In response, the BBC said:
"The BBC aims to make its content as widely available as possible and has always taken a platform agnostic approach to its internet services.
"It is not possible to put an exact timeframe on when BBC iPlayer will be available for Mac users. However, we are working to ensure this happens as soon as possible and the BBC Trust will be monitoring progress on a six monthly basis."