Stating concerns about Google’s dominance in the mobile advertising market and lack of competition, two consumer groups have asked the Federal Trade Commission to block Google’s $750 million acquisition of AdMob.

In a joint letter to the FTC, Consumer Watchdog and the Center for Digital Democracy said Google (NSDQ: GOOG) argued that Google is buying its way to dominance in the mobile advertising, by diminishing the competition “to the detriment of consumers.” In the letter, the two agencies wrote: “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,” according to a press release. More interestingly, the two groups said the deal raises substantial privacy concerns because both companies gather tremendous amounts of data about consumers’ online behavior, including their location.