A conflict has erupted between Google and Microsoft over the Windows Phone YouTube app.
Google has blocked users from watching videos via the app, saying it violated its terms of service.
Microsoft had failed to make the app compatible with HTML5, which was what YouTube had originally requested. Microsoft said the issues were "manufactured" and Google was deliberately hindering the Windows Phone platform.
In a blog post entitled 'The limits of Google's openness', Microsoft lawyer David Howard requested that Google lift the block, and outlined his company's issues with the stance.
"The roadblocks Google has set up are impossible to overcome, and they know it," said Howard.
"Google's objections to our app are not only inconsistent with Google's own commitment of openness, but also involve requirements for a Windows Phone app that it doesn't impose on its own platform or Apple's."
He said: "It seems to us that Google's reasons for blocking our app are manufactured so that we can't give our users the same experience Android and iPhone users are getting.
In a statement, Google defended its actions: "Unfortunately, Microsoft has not made the browser upgrades necessary to enable a fully featured YouTube experience, and has instead re-released a YouTube app that violates our terms of service. It has been disabled.
"We value our broad developer community and therefore ask everyone to adhere to the same guidelines."
The Windows Phone platform is, according to some metrics, the third most popular mobile operating system in use worldwide.