Two consumer groups Monday asked the Federal Trade Commission to block Google's $750 million deal to acquire mobile advertising firm, AdMob, on anti-trust grounds.

In a joint letter to the FTC, Consumer Watchdog and the Center for Digital Democracy (CDD) said Google is simply buying its way to dominance in the mobile advertising market, reducing competition to the detriment of consumers.

"The mobile sector is the next frontier of the digital revolution. Without vigorous competition and strong privacy guarantees this vital and growing segment of the online economy will be stifled," wrote John M. Simpson, consumer advocate at Consumer Watchdog and CDD Executive Director Jeffery A. Chester.

"Consumers will face higher prices, less innovation and fewer choices. The FTC should conduct the appropriate investigation, block the proposed Google/AdMob deal, and also address the privacy issues."

Last week Google said the FTC had made a second request for additional information about the deal, a signal the commission is closely examining the proposal.

In addition to the anti-trust issues, the letter from the two non-partisan, non-profit groups, said a combined Google/AdMob raises privacy concerns. Both AdMob and Google gather large amounts of data about consumers' online behavior, including their location.

"Permitting the expansion of mobile advertising through the combination of these two market leaders without requiring privacy guarantees poses a serious threat to consumers," the letter said.

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