A bitter row has broken out 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.
The search company had requested the app be made using HTML5 code language, but Microsoft said it was unable to.
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.
"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 added: "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.
"The roadblocks Google has set up are impossible to overcome, and they know it."
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.
However, it lags well behind Google's Android and Apple's iOS.
As a result, there are considerably fewer apps available for Windows Phone. To address this, Microsoft is investing its own resources to bring some key services to its platform.
In May, Microsoft's first attempt at creating a YouTube app was blocked after Google complained it failed to display ads correctly.
The companies agreed to work together to devise a new version, but Google insisted it was created using HTML5, an open web coding standard, rather than code specific to the Windows Phone platform.
Mr Howard said this was an "odd request", and one that was unfair to Microsoft.
"Neither YouTube's iPhone app nor its Android app are built on HTML5," he wrote.
"Nevertheless, we dedicated significant engineering resources to examine the possibility.
"At the end of the day, experts from both companies recognised that building a YouTube app based on HTML5 would be technically difficult and time-consuming, which is why we assume YouTube has not yet made the conversion for its iPhone and Android apps."