The Obama FBI not only presented the infamous Steele dossier to a secret court knowing it was unverified, the bureau continued using the document after the purported source declared its claims were "garbage," said Attorney General William Barr at an event in Washington on Tuesday.

"They were told they didn't have probable cause to get a warrant. And so they took the Steele dossier, which they had done nothing to verify, and they used that to get the warrant," Barr said at The Wall Street Journal CEO Council gathering, referring to FBI officials.

The attorney general was highlighting findings of Justice Department Inspector General Michael Horowitz's report, released Monday, on the Obama administration's surveillance of the Trump campaign in its 2016 counter-intelligence probe of alleged collusion with Russia.

Barr, who has launched what is now a criminal investigation of the origins of the Trump-Russia collusion probe, said the FBI continued to withhold from the FISA court exculpatory information as well as evidence of Steele's lack of reliability.

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But the "major takeaway," he said, is that when the FBI finally got around to talking to Steele's "primary subsource" for the information in the dossier, agents discovered the source regarded Steele's claim as, in Barr's words, "garbage."

Barr paraphrased the source telling the FBI: "I don't know what Steele is talking about. I didn't tell him this stuff. It was mostly barroom talk and rumor. I made it clear to him this was my own suppositions and theories."

"At that point," Barr said, "it was clear that the dossier was a sham."

Nevertheless, the FBI continued to obtain FISA warrants based on the dossier.

"And more damning," Barr said, "is that they actually filed with the court saying, 'We talked to the subsource and we found him credible and cooperative.'"

What the subsource "was being truthful about," the attorney general said, "is that the dossier is garbage."

"It's hard to look at this stuff and not think that it was a gross abuse," he said at the Wall Street Journal event.

Barr said he disagreed with Horowitz's conclusion that the FBI had an adequate basis to open its probe of the Trump campaign and found no evidence that political bias influenced the inquiry.

In an interview with NBC News, Barr said the nation "was turned on its head for three years" based on "a completely bogus narrative that was largely fanned and hyped by a irresponsible press."

Barr said the 17 significant "errors or omissions" by the FBI cited in the Horowitz report regarding the warrants to surveil Trump campaign adviser Carter Page "were not satisfactorily explained."

Horowitz wrote that he "did not find documentary or testimonial evidence that political bias or improper motivation influenced the decisions."

"All [Horowitz] said is that people gave me an explanation, and I didn't find anything to contradict it, so I don't have a basis for saying that there was improper motive," Barr said.

"But he hasn't decided the issue of improper motive," he said, referring to the inspector general.

"Have you?" Barr was asked.

"No," he replied.

Will Comey and McCabe be held accountable?

The attorney general was asked whether "people will be held accountable" for their actions, including former FBI Director James Comey and former Deputy Director Andrew McCabe.

Barr said he would not speculate exactly who will be held accountable, but he indicated that the top two bureau officials bore responsibility.

"I've said that I think there was a failure of leadership," he said. I'll just quote the IG."

Horowitz, Barr said, "says that the explanations he received were not satisfactory."

"Now, when you have the kind of rank behavior that that involved, and the IG says he doesn't get an explanation for it, you can draw your own conclusions from that."