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 dispute first started in May, when YouTube Director of Global Platform Partnerships Francisco Varela sent a cease-and-desist letter to Todd Brix, GM of Windows Phone Apps, demanding that the his company take down the Microsoft-authored app. The letter claims that the application allows users to download videos from YouTube, while also stripping ads from the videos that it displays. It also shows videos that have been restricted from playback on certain platforms (like when the video owner doesn’t give YouTube the right to display videos on mobile phones or tablets).

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. Microsoft made the unprecedented decision to author a Youtube app on its own after YouTube refused to devote any of its resources to supporting Windows Phone devices with an approved native app.

In May, Microsoft released a full YouTube app for Windows Phone with functionality that rivaled the official apps on Android and iOS, but was told shortly after to remove it.

Instead of pulling the application like Google requested, Microsoft pushed out an update on the very day Google demanded it be removed. The update resolved the download option but did not address the lack of ads. Days later, the pair released a joint statement promising an updated YouTube app with ads, and compliance with YouTube’s API terms of service.

Instead of waiting for Google's approval, Microsoft sent Google an updated app with ad support last week, and immediately published the new application to the Windows Phone Store. Google responded by revoking an essential API key that Microsoft was using, blocking access to YouTube from the app.

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."

Google appears to be forcing Microsoft into a tricky situation; but it is one that Microsoft brought upon itself by teasing its users with a YouTube app that wasn't approved in the first place. At the same time it has every right to control, manage, and protect its own brands and services in the same way Microsoft does, providing it's not anti-competitive.

Whilst the two tech giants battle out the issue, it seems the people who are getting hurt are the users. There are many users showing their frustration and annoyance at the broken Windows Youtube app on the Windows store pages. It would seem many users are not even aware of the dispute or the reason the Youtube app no longer works correctly.