Microsoft updated its own YouTube application for Windows Phone just over a week ago and Google isn't impressed. The Verge has obtained a copy of a cease and desist letter that Google has sent to Microsoft recently, demanding that Microsoft "immediately withdraw this application from the Windows Phone Store and disable existing downloads of the application by Wednesday, May 22, 2013." Microsoft's YouTube app for Windows Phone appears to have taken Google by surprise.

Windows Phone app violates API use

Google's complaint centers on the lack of ads in Microsoft's YouTube app, something it claims is a direct violation of the terms and conditions of the company's YouTube API. The Verge has learned that Microsoft created the app without Google's consent with features that specifically prevent ads from playing. The lack of ads clearly hits Google's own revenues, but also those of its third-party content creators that are paid through the company's AdSense program. "Unfortunately, by blocking advertising and allowing downloads of videos, your application cuts off a valuable ongoing revenue source for creators, and causes harm to the thriving content ecosystem on YouTube," says Google's letter, addressed to Microsoft's Todd Brix.

Microsoft has previously complained to the EU over Google's apparent refusal to let Windows Phone access YouTube metadata. While it initially seemed like both companies had reconciled their differences, that's clearly not the case. On stage at Google I/O today, CEO Larry Page detailed his take on technology's future, noting that industry negativity is holding back progress. Page told an audience member that "we struggle with people like Microsoft."

All the bickering means customers lose out

The relationship is clearly strained with campaigns like Scroogled, and the YouTube complaint is the latest in a set of issues between both companies. In December, Google announced its plans to drop Exchange ActiveSync support, a decision that left Microsoft sweating over its lack of the alternative CalDAV and CardDAV protocol support for Windows Phone. Despite this, it's clear the pair can work together on certain interperability. Just this week, Microsoft announced its plans to support Google Talk within Outlook.com, a change that's beneficial for consumers of both company's services.

For now, it appears that Windows Phone YouTube users will have to utilize unofficial third-party apps or settle for Google's mobile web version. Until Microsoft and Google can collaborate without bickering, it's the customers of both companies that lose out.

The Verge has reached out to Microsoft for comment on Google's cease and desist letter and we'll update you accordingly.

Update: Microsoft has responded to Google's demands, welcoming the addition of ads.