Last week, we covered the Department of Justice's move to block AT&T's proposed acquisition of T-Mobile, the fourth-largest wireless carrier in the United States. On Tuesday, Sprint joined the battle on the government's side. The nation's third-largest wireless carrier brought suit against its rivals, calling their merger "brazenly anticompetitive" and arguing that it would violate antitrust law.

"AT&T would be removing a low price and innovative maverick competitor that provides particularly disruptive competition in the marketplace," Sprint argues in its complaint. "The ultimate and predictable effect of the proposed transaction would be to tip the US wireless industry effectively toward a duopoly controlled by AT&T and Verizon.

"The wireless industry is far too important to the US economy to give gate-keeper control over it to the Twin Bells," the complaint says.

In a statement, Sprint's Susan Haller said that Sprint was bringing its lawsuit "on behalf of consumers and competition." She said Sprint wanted to "contribute our expertise and resources" to helping the government win its case.

This is not the first time Sprint has voiced objections to its competitors' merger. The carrier started complaining almost immediately after the deal was announced, and has been pressing the FCC to stop the transaction. In a May filing with the FCC, Sprint warned that approving the merger would "let the wireless industry regress inexorably toward a 1980s-style duopoly."

AT&T expressed surprise when the government announced its opposition last week, and pledged to "vigorously contest" the lawsuit. Presumably, it will fight Sprint's lawsuit with equal vigor.

Listing image by Photograph by William Ross