Google recently announced plans to buy Admob for $750 million. In response, Consumer Watchdog and the Center for Digital Democracy have jointly sent the FTC a letter asserting that Google seeks to use its financial clout to dominate the mobile advertising market and reduce competition, which would be detrimental to consumers.

The letter includes an assertion that consumers will face higher prices, less innovation and fewer choices, and adds: "The FTC should conduct the appropriate investigation, block the proposed Google/AdMob deal, and also address the privacy issues."

Google has confirmed that the FTC has requested additional information about the deal, suggesting that the commission is examining the deal closely. The company has rejected criticism of the acquisition plan and denies that it would stifle competition. Google spokesman Adam Kovacevich commented: "There are more than a dozen mobile ad networks and this deal is similar to mobile advertising acquisitions that AOL, Microsoft and Yahoo have made in the past two years."

The complaint to the FTC follows hot on the heals of news that mobile social network Yelp has abandoned negotiations on a Google take-over. Talks had reached the stage where both companies had confirmed that the deal price would be $550 million plus earnouts, and only the final details of the acquisition had to be agreed.