Former U.S. Attorney Joe diGenova delivered blistering criticism of the Justice Department watchdog’s report on how the FBI obtained Foreign Intelligence Surveillance Act warrants to monitor a former Trump campaign adviser.

DiGenova, a vocal Trump defender who had predicted the report would be “explosive” and ruin the careers of top officials in the FBI and Justice Department, was astonished by Inspector General Michael Horowitz’s assessment.

“Horowitz’s conclusions are absolutely outrageous,” diGenova told Fox Business host Lou Dobbs on Monday.

The focus of Horowitz's investigation was into allegations of surveillance abuse against former Trump campaign adviser Carter Page. The inspector general found errors and omissions were made in the process but did not establish that political bias tainted officials' actions over the course of the Russia investigation.

Horowitz also determined there was sufficient cause for the FBI's counterintelligence investigation into the Trump campaign. But both U.S. Attorney John Durham, who is conducting a separate investigation into the origins of the Russia investigation, publicly disagreed with that conclusion.

“Durham felt he had to slap Horowitz right across the face publicly. That’s quite embarrassing for Horowitz. That is a rebuke like I have never seen of an inspector general by a United States attorney, and well deserved may I say,” diGenova said.

Only one known criminal referral to Durham stems from Horowitz's investigation, related to an FBI lawyer who altered a document in the process of obtaining a FISA warrant renewal against Page.