The BBC has been accused of forcing people to use Microsoft operating systems and has been threatened with a complaint to the European Commission.
The iPlayer will allow viewers to catch up with Life on Mars
The charge concerns the use of Microsoft technology in the corporation's forthcoming iPlayer.
The web service, set for launch later this year, allows viewers to watch shows up to 30 days after broadcast.
The BBC has said it does intend to allow access to its content from computers with other operating systems.
A statement from the organisation read: "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."
The accusations against the BBC have been made by advocacy group the Open Source Consortium (OSC).
They argue that the iPlayer will force people to use and purchase Microsoft products because it will initially only work on Microsoft Windows computers. This would give the software company an unfair advantage and would be uncompetitive, they say.
iPlayer will allow viewers to catch up on TV programmes for seven days
Some TV series can be downloaded and stored for 30 days
Viewers will be able to watch shows streamed live over the internet
Users will not be able to download programmes from other broadcasters
Classical recordings and book-readings are excluded from iPlayer
The OSC would like to see the iPlayer use formats that work on all operating systems. "The BBC has a mandate to provide equal access to people irrespective of platform," said Mark Taylor, president of OSC.
"We don't think it is appropriate to lock people into a particular desktop technology."
The OSC has compared the situation to the BBC offering programmes that only work on certain makes of television.
"We believe the BBC has a higher duty of care than a purely commercial organisation," Mr Taylor told the BBC News website.
The group, composed of organisations, businesses and individual proponents of open source software, has already complained to the telecoms and broadcast regulator Ofcom, as well as the DTI and BBC Trust.
Ofcom have previously stated that access to the iPlayer be "only one of many factors influencing the decision to purchase a new computer [or] operating system.
However, OSC disagrees and says the next step is to make a formal complaint to the European Commission (EC).
"We're preparing the full details at the moment and we will be sending a formal letter within the next week," said Mr Taylor.
The EC will then have to decide whether there is a case to answer.
The Windows-only media player was approved by the BBC Trust at the end of April this year. The BBC had initially chosen to concentrate on a Windows-based system as it is the world's dominant operating system.
The BBC intends to make content available on all platforms
In addition, it allows the corporation to use Microsoft's off-the-shelf Digital Rights Management (DRM) system that means the programmes are deleted after 30 days.
All programmes, once downloaded, are only playable within iPlayer or using Windows Media Player 10 or 11.
The DRM also prevents them being copied to other mediums such as DVD.
When the broadband player was approved, the corporation's governing body asked the BBC to ensure that the iPlayer could run on different systems - such as Apple Macs - within "a reasonable time frame", initially twenty-four months.
The BBC has previously said it cannot commit to a two-year time frame as many decisions would have to be made by third parties.
A statement from the BBC read: "Our ability to deliver this open approach will be influenced by the availability of alternative DRM systems on the market.
"In order to maximise public value, the BBC must balance extending access to content with the need to maintain the interests of rights holders and the value of secondary rights in BBC programming. Without a time-based DRM framework the BBC would not be able to meet the terms of the trust's PVT (Public Value Test) decision."
However, the OSC argue that DRM-free downloads would be in the "public interest".
"In an ideal world all DRM would be removed," said Mr Taylor.