Google has formally demanded that Microsoft yank its new YouTube app for Windows Phone, which allows users to skip ads and download YouTube videos — both of which violate YouTube’s terms of service. The Verge has the full text of Google’s cease-and-desist letter, which is dated today.

ReadWrite reported on the Microsoft app’s apparent rule-breaking last week.

Updated 10:24am PT on May 16: A Microsoft PR representative emailed us a statement in response to Google’s letter:

YouTube is consistently one of the top apps downloaded by smartphone users on all platforms, but Google has refused to work with us to develop an app on par with the apps for other platforms. Since we updated the YouTube app to ensure our mutual customers a similar YouTube experience, ratings and feedback have been overwhelmingly positive. We’d be more than happy to include advertising but need Google to provide us access to the necessary APIs. In light of Larry Page’s comments today calling for more interoperability and less negativity, we look forward to solving this matter together for our mutual customers.