Rep. Darrell Issa vowed to continue pursuing a civil lawsuit to compel Attorney General Eric Holder to hand over more documents related to Operation Fast and Furious.
Kenneth Melson, the acting ATF director during the operation, also resigned. He had been reassigned to another position.
The report largely spared Holder from personal blame, saying he did not authorize the tactics used and did not know about allegations that guns had "walked" until after the DOJ broadly denied that tactic was used in a February letter to Sen. Chuck Grassley (R-Iowa).
"I hope today's report acts as a reminder of the dangers of adopting as fact unsubstantiated conclusions before an investigation of the circumstances is completed," Holder said in a statement.
But the report strongly criticized other senior officials, including Lanny Breuer, head of the department's criminal division.
Breuer, the report said, should have alerted Holder or his second-in- command when he learned guns had walked in Wide Receiver.
Regarding the Feb. 4 letter to Grassley that denied guns had "walked" in Fast and Furious, the report said several senior officials claimed to the letter's drafters that such tactics had not been used, even though they had been presented with information that should have caused concern.
In particular, William Hoover, the former second-ranking ATF official, and former U.S. Attorney Dennis Burke both adamantly denied to DOJ colleagues that guns had walked when both had considerable knowledge about the operation, the report said.
Evidence "strongly suggests" that Burke provided information he knew was false to colleagues, which the report said was "irresponsible."
The report was even more critical of a letter sent on May 2, 2011, that reiterated the broad denial even as more information about the operation became public and was learned internally at the DOJ.
By then, senior officials "knew or should have known" that the broad denial was false," the report said.
The DOJ ultimately rescinded the February letter 11 months after it was sent, conceding it contained inaccurate information.
For their part, Congressional Democrats seized on findings in the report showing that some of the more flamboyant allegations made in relation to Fast and Furious were not true.
"The IG's comprehensive report debunks many of the extreme allegations made by Republicans and confirms many of the conclusions reached in a report I issued nearly a year ago," said Rep. Elijah Cummings (D-Md.), ranking member of the Oversight panel.
Vice President Joe Biden waits to conduct a mock swearing-in ceremony with Sen. Brian Schatz, D-Hawaii, in the Capitol's Old Senate Chamber, December 2, 2014. Schatz was sworn in to serve the remainder of his term since he was appointed to the seat after Sen. Daniel Inouye, D-Hawaii, passed away.