A new report by an internal watchdog at the Department of Justice on the gun running operation known as Fast and Furious will lead to the departure of at least two senior officials, and possible discipline for as many as a dozen more.

The 512 page report issued on Wednesday afternoon backs up many of the arguments of U.S. Attorney General Eric Holder, finding that he did not know key details of the operation and was kept in the dark by lower level staff.

The report cites a "lack of meaningful oversight" by officials at the bureau of Alcohol, Tobacco and Firearms (ATF), as the ex-Acting Director of that agency is one official who will no longer be working for the Justice Department.

As for how the Justice Department delivered information to Congress about the operation, the report found that some statements made to lawmakers were "not accurate," and that one key letter sent to lawmakers contained "distorted" information because of "questionable judgments."

The report also found that officials had sent "narrowly drawn" denials to Sen. Charles Grassley (R-IA), who had repeatedly asked for information about Fast and Furious.

"Operation Fast and Furious was the height of irresponsibility on the part of a number of people from the ATF Phoenix field office all the way up to the Justice Department headquarters," Grassley said in a statement.

Grassley bemoaned the lack of oversight when the Justice Department was facing difficult questions.

"It took the death of our own Border Patrol Agent, action by a courageous whistleblower, and intense scrutiny from Congress before they even took note of what was happening under their own eyes," said Grassley.