Sprint has been one of the most outspoken opponents of AT&T's proposed acquisition of T-Mobile ever since the deal was announced back in March. Today the Now Network further cemented its stand against the merger, filing suit in attempt to have it blocked. The lawsuit, which has been brought against AT&T, AT&T Mobility, Deutsche Telekom, and T-Mobile, alleges that AT&T's acquisition of T-Mobile would be a violation of Section 7 of the Clayton Antitrust Act and that it would do harm to consumers and competition here in the U.S. Sprint specifically claims that a combined AT&T-Mobile would:

• Harm retail consumers and corporate customers by causing higher prices and less innovation.
• Entrench the duopoly control of AT&T and Verizon, the two "Ma Bell" descendants, of the almost one-quarter of a trillion dollar wireless market. As a result of the transaction, AT&T and Verizon would control more than three-quarters of that market and 90 percent of the profits.
• Harm Sprint and the other independent wireless carriers. If the transaction were to be allowed, a combined AT&T and T-Mobile would have the ability to use its control over backhaul, roaming and spectrum, and its increased market position to exclude competitors, raise their costs, restrict their access to handsets, damage their businesses and ultimately to lessen competition.

This lawsuit comes less than a week after the U.S. Department of Justice filed suit against AT&T's buyout of T-Mobile. Sprint's suit has been filed in a Washington D.C. court as a related case to the DoJ's complaint. Considering how strongly the Now Network has opposed the AT&T-Mobile deal, it's not much of a surprise to see Sprint take the next step in its fight and file suit alongside the Department of Justice. Neither AT&T nor T-Mobile has commented on Sprint's suit, but we'll update you if they do.

UPDATE: AT&T has issued a response to Sprint's lawsuit, saying that it will "vigorously contest this matter in court." The full statement is as follows:

"AT&T Statement on 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."

Sprint Files Suit to Block Proposed AT&T and T-Mobile Transaction
WASHINGTON (BUSINESS WIRE), September 06, 2011 - Sprint Nextel [NYSE:S] today brought suit against AT&T, Inc., AT&T Mobility, Deutsche Telekom and T-Mobile seeking to block the proposed acquisition as a violation of Section 7 of the Clayton Act. The lawsuit was filed in federal court in the District of Columbia as a related case to the Department of Justice’s (DOJ) suit against the proposed acquisition.

“Sprint opposes AT&T’s proposed takeover of T-Mobile,” said Susan Z. Haller, vice president-Litigation, Sprint. “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.”

Sprint’s lawsuit focuses on the competitive and consumer harms which would result from a takeover of T-Mobile by AT&T. The proposed takeover would:

Harm retail consumers and corporate customers by causing higher prices and less innovation.
Entrench the duopoly control of AT&T and Verizon, the two "Ma Bell" descendants, of the almost one-quarter of a trillion dollar wireless market. As a result of the transaction, AT&T and Verizon would control more than three-quarters of that market and 90 percent of the profits.
Harm Sprint and the other independent wireless carriers. If the transaction were to be allowed, a combined AT&T and T-Mobile would have the ability to use its control over backhaul, roaming and spectrum, and its increased market position to exclude competitors, raise their costs, restrict their access to handsets, damage their businesses and ultimately to lessen competition.
About Sprint Nextel

Sprint Nextel offers a comprehensive range of wireless and wireline communications services bringing the freedom of mobility to consumers, businesses and government users. Sprint Nextel served more than 52 million customers at the end of 2Q 2011 and is widely recognized for developing, engineering and deploying innovative technologies, including the first wireless 4G service from a national carrier in the United States; offering industry-leading mobile data services, leading prepaid brands including Virgin Mobile USA, Boost Mobile, and Assurance Wireless; instant national and international push-to-talk capabilities; and a global Tier 1 Internet backbone. Newsweek ranked Sprint No. 6 in its 2010 Green Rankings, listing it as one of the nation’s greenest companies, the highest of any telecommunications company. You can learn more and visit Sprint at www.sprint.com or www.facebook.com/sprint and www.twitter.com/sprint.