• by Mark Walsh  @markfwal, September 6, 2011

Sprint has filed suit to block AT&T’s proposed $39 billion acquisition of T-Mobile just days after the U.S. government moved to stop the transaction on antitrust grounds. In its own legal challenge, the nation’s No. 3 carrier argues the deal would hurt consumers and lead to duopoly control by the two largest wireless operators—AT&T and Verizon.

Sprint has been one of the most vocal critics of the acquisition since AT&T announced its plans to purchase T-Mobile in March.

The Department of Justice filed its action Aug. 31, saying the combination of AT&T and T-Mobile would “substantially lessen competition” in the wireless industry and could lead to higher prices, poorer quality service and fewer innovative products. The government is seeking an injunction against the merger.

Besides harming consumers, Sprint said in a statement today the deal would also give AT&T and T-Mobile an unfair advantage over Sprint and other independent carriers.

“Sprint opposes AT&T’s proposed takeover of T-Mobile,” said Susan Z. Haller, vice president-litigation, at Sprint, said in a statement. “With today’s legal action, we are continuing that advocacy on behalf of consumers and competition, and expect to contribute our expertise and resources in proving that the proposed transaction is illegal.”

AT&T has vowed to fight the DOJ suit, maintaining the merger would benefit consumers by providing improved and expanded services for millions of mobile users and create tens of thousands of jobs. AT&T hadn’t immediately issued a statement on the Sprint suit Tuesday.

Update: AT&T issued this statement Tuesday afternoon in response to the Sprint lawsuit:

"This simply demonstrates what we’ve said all along – Sprint is more interested in protecting itself than it is in promoting competition that benefits consumers. We of course will vigorously contest this matter in court as AT&T’s merger with T-Mobile USA will: help solve our nation’s spectrum exhaust situation and improve wireless service for millions; allow AT&T to expand 4G LTE mobile broadband to another 55 million Americans, or 97% of the population; and result in billions of additional investment and tens of thousands of jobs, at a time when our nation needs them most."

The Federal Communications Commission, whose approval is required for the AT&T-T-Mobile merger to go forward, hasn’t yet weighed in on the matter. But FCC Chairman Julius Genachowski last week said the deal, “raises serious concerns about the impact of the proposed transaction on competition.”