The Federal Communications Commission has launched a sweeping inquiry into Apple’s recent rejection of Google’s telephony application for the iPhone, Google Voice.

The FCC on Friday sent letters of inquiry to Apple, AT&T and Google in an effort to understand the relationship between the companies with regard to Apple’s application approval process for its App Store. 

The move is the latest in FCC efforts to gauge competition in the wireless industry.

The letters pose a range of questions related to the App Store’s practices. More specifically, the FCC questions the approval criteria for applications submitted to Apple’s popular App Store and whether AT&T had any involvement in the rejection of the Google Voice application.

FCC Chairman Julius Genachowski said Friday that the move was an effort to obtain information and protect consumers.

“The Wireless Bureau’s inquiry letters to these companies about their practices reflect the Commission’s proactive approach to getting the facts and data necessary to make the best policy decisions on behalf of the American people,” he wrote.

Apple was not available for comment before press time, but blame for the rejection has been passed around in recent days. According to some reports, Apple said that it rejected the app due to Google Voice’s duplication of services offered by AT&T, such as text messaging.

A spokeswoman for AT&T was referring reporters to Apple, saying that “AT&T doesn’t manage or approve applications and has received the FCC letter and will respond accordingly.”

Another similar third-party application, GV Voice, was also rejected by Apple.

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