U.S. Attorney General William Barr and U.S. President Donald Trump attend a signing ceremony for an executive order in the Oval Office of the White House on November 26, 2019 in Washington, DC.

Attorney General William Barr said that he still believes that FBI operated in "bad faith" in its investigation of possible Russian coordination with Donald Trump's 2016 campaign, a day after the Justice Department's internal watchdog found no evidence of political bias in the opening of the probe.

"I think our nation was turned on its head for three years based on a completely bogus narrative that was largely fanned and hyped by an irresponsible press," Barr told NBC News' Pete Williams in an interview that aired Tuesday.

Barr said that he believes there were "gross abuses" and "inexplicable behavior" by the FBI related to the probe that "leaves open the possibility that there was bad faith."

The report released Monday by DOJ Inspector General Michael Horowitz is the product of a yearslong investigation involving dozens of interviews and more than a million documents.

It concludes that it "did not find documentary or testimonial evidence that political bias or improper motivation influenced the decisions to open" the Trump-Russia probe.

But it did find "serious performance failures" made by some agents in charge of the surveillance applications submitted to the U.S. Foreign Intelligence Surveillance Court.

Those failures included numerous "factual misstatements omissions" found in the review — some more significant than others, the report said, but when "taken together resulted in [surveillance] applications that made it appear that the information supporting probable cause was stronger than was actually the case."

Barr said in a statement released after Horowitz's report came out that it "now makes clear that the FBI launched an intrusive investigation of a U.S. presidential campaign on the thinnest of suspicions that, in my view, were insufficient to justify the steps taken."

Barr's statement drew new accusations from critics who say he is spinning the conclusions of the report to defend Trump.

He was blasted in April for asserting that he believed "spying did occur" by the FBI toward the Trump campaign. In his interview with NBC, Barr said that Trump's campaign "was clearly spied upon. That's what electronic surveillance is."

Barr has opened his own investigation into the origins of the Trump-Russia probe, despite Horowitz's inquiry being well underway when Barr was confirmed as attorney general.

U.S. Attorney John Durham, whom Barr appointed to head that investigation, said in a statement Monday that "while our investigation is ongoing, last month we advised the Inspector General that we do not agree with some of the report's conclusions as to predication and how the FBI case was opened."

Barr told NBC that the statement was "necessary to avoid public confusion" being pushed by the press "that the issue of predication was sort of done and over."