AT&T has denied that it interfered in the rejection of the Google Voice iPhone application. And Apple said that it was still reviewing the decision.

Google Voice has not been approved for distribution to the iPhone, and on 31 July, the US telecoms watchdog the FCC questioned Apple and AT&T about their treatment of that and other proposed iPhone applications. It also questioned Google about its iPhone application and the approval process for software on its own Android mobile platform. All three companies submitted responses on Friday.

Apple said it had not rejected the Google Voice iPhone application but is still studying it. In response to pointed questions, both Apple and AT&T said the iPhone maker did not consult AT&T about Google Voice and that the carrier has not been involved in evaluating it. They said Apple typically does not consult AT&T about decisions on what applications can be offered in the iPhone App Store.

Google Voice would let users make calls on the smartphone while also providing voicemail, text messaging and contact management features. The fact that it has not been approved for the iPhone has heightened criticism of the review process for iPhone applications, which critics say is murky and unpredictable.

In the case of Google Voice, some observers suspected AT&T had squelched the software because it feared competition for its own voice services. In questioning the companies, the FCC cited pending proceedings at the agency concerning open access to wireless networks and exclusive deals between handset makers and carriers.

Apple told the FCC that Google Voice hasn't been approved because it appears to replace the iPhone's core phone functionality and user interface with its own interface for phone calls, text messaging and voicemail. The application also transfers the user's Contacts database to Google's servers, "and we have yet to obtain any assurances from Google that this data will only be used in appropriate ways," Apple wrote.

The FCC had also questioned Apple and AT&T about third-party applications that make use of Google Voice. Along with Google Voice, three other applications - GVDialer from MobileMax, VoiceCentral from Riverturn and GV Mobile by Sean Kovacs - also raise issues that Apple is still studying, the company wrote.