The recklessness of federal officials in their harebrained scheme to assist in illegal gunrunning to Mexican drug cartels was laid bare in a scathing report by the Justice Department’s inspector general. Primary blame for the botched program — known as Operation Fast and Furious — was placed on a group of Arizona-based prosecutors and officials of the Bureau of Alcohol, Tobacco, Firearms and Explosives who lost track of hundreds of weapons that were allowed to pass into Mexico in hopes of tracing them to cartel leaders.

Two of the high-powered guns turned up at an Arizona shootout in 2010 that killed an American Border Patrol officer. The ill-conceived operation put public safety at risk with no effective plan to track the guns, according to the inspector general, Michael Horowitz, who found “misguided strategies, tactics, errors in judgment and management failures,” including slipshod oversight at Justice Department headquarters in Washington.

But the report said there was no evidence that Attorney General Eric Holder Jr. knew of the risky operation until after it was shut down in 2011. While several high-ranking officials responsible for the fiasco have resigned or retired, the report recommended at least a dozen current Justice Department and A.T.F. officials for further investigation for possible disciplinary action.

House Republicans, in a fiercely partisan confrontation with the Justice Department, foolishly cited Mr. Holder for contempt in June for resisting some of their demands for documents. They should have waited for the report, which confirmed some of their criticisms but exonerated Mr. Holder and found no evidence for bizarre allegations that Operation Fast and Furious was a scheme designed to justify tougher federal gun controls, not penetrate drug cartels. In fact, the operation was similar to a gun-trafficking program in 2006 run by officials in the Bush administration.