The US Justice Department has referred 14 of its employees for possible internal discipline in connection with a botched operation that allowed thousands of guns to fall into the hands of Mexican drug cartels.
Wednesday's report into the strategy followed a 19-month review by the department's inspector general into Operation Fast and Furious, an anti-gun-trafficking effort which allowed the firearms to cross the border into Mexico.
The operation angered US gun-rights advocates and is a focal point for Republican criticism of President Barack Obama leading up to the November 6 election.
Operation Fast and Furious involved "gun-walking," by Arizona agents from the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), an experimental tactic barred under long-standing department policy.
The agents allowed suspected straw purchasers, in these cases believed to be working for Mexican drug gangs, to leave Phoenix-area gun stores with weapons in order to track them and bring charges against gun-smuggling kingpins who had long eluded prosecution, but they lost track of most of the guns.
Senior Justice Department official Lanny Breuer, an Obama appointee and the head of the department's criminal division, is cited in the report for not alerting his superiors in 2010 to flaws in a similar programme, Operation Wide Receiver, that was started during George W Bush's presidency.
The report concluded there is "no evidence" that Attorney General Eric Holder, who heads the Justice Department, knew the details of Fast and Furious before they became publicly known in February 2011.
Holder requested the internal review the same month.
Jason Weinstein, one of Breuer's aides, whom the report also refers for possible disciplinary action, has resigned from the department, a spokeswoman said on Wednesday.
Weinstein failed to question firearms officials about the questionable tactics they used, the report said.
Kenneth Melson, another senior official, will retire from the Justice Department, the spokeswoman said.
Melson was the acting director of the ATF until 2011, when he was reassigned.
Fast and Furious came to light after the December 2010 shooting to death of Brian Terry, a US border patrol agent.
Two guns that firearms agents attempted to track were found at the scene of Terry's death in rural Arizona.
The inspector general's report was a form of validation for the Republican-led investigation, saying lower-level officials should have briefed Holder about the investigation much earlier.
Fast and Furious has produced charges against 20 gun traffickers, 14 of whom have pleaded guilty so far.