Attorney General William Barr said the Justice Department is reviewing the “very unusual” role that the so-called Steele dossier played in the Trump-Russia investigation.

In a Fox News interview that aired Friday, Barr said there were "clear mistakes" in the anti-Trump research. The government’s use of the dossier, whose unverified allegations were used to justify surveillance of a former Trump campaign associate, is “one of the questions that we’re going to have to look at” as part of his broader probe into the actions taken by the DOJ and FBI.

The dossier was authored by British ex-spy Christopher Steele and was packed with unverified claims about President Trump's ties to Russia. It formed a key part of the Foreign Intelligence Surveillance Act applications used to justify surveillance warrants against former Trump campaign adviser Carter Page. Steele was working for Fusion GPS which was receiving funding through the Perkins Coie law firm from the Clinton campaign and the Democratic National Committee — facts that were not communicated to the Foreign Intelligence Surveillance Court.

Barr said that “it’s a very unusual situation to have opposition research like that — especially one that on its face had a number of clear mistakes and a somewhat jejune analysis.” Barr’s pointed critiques of the Steele dossier’s flaws comes after former FBI Director James Comey and former FBI General Counsel James Baker defended their handling of the dossier in recent days.

Comey said “the most important part” of the dossier was related to “Russians coming for the American election,” which he asserted was “consistent with our other intelligence” and “true.” Baker said the FBI treated the dossier “seriously … but not literally.”

Although Barr did not discuss the specific mistakes he was referring to in the dossier, it is likely that he was referring to newly released notes from an Oct. 11, 2016, meeting between Steele and former Deputy Assistant Secretary of State Kathleen Kavalec, which cast doubt on the reliability of Steele’s dossier and called into question the information provided to the court in the FISA application that was submitted later that month. The notes, which Kavalec is believed to have emailed to the FBI in mid-October, indicate that Steele knew he had been hired by the Clinton campaign and the Democratic National Committee and had been told they wanted his findings made public prior to the 2016 election on Nov. 8.

The notes also show that Kavalec believed at least some of Steele’s allegations to be false. She said Steele alleged that, as part of Russia’s 2016 election interference efforts, there was a “significant Russian network in the U.S. run by the Russian Embassy that draws on emigres to do hacking and recruiting” and “payments to those recruited are made out of the Russian Consulate in Miami.” But Kavalec pointed out “it is important to note that there is no Russian Consulate in Miami.”

The Wall Street Journal reported earlier in May that DOJ Inspector General Michael Horowitz “is homing in on” and “has been asking witnesses about” the FBI’s “treatment of information” provided by Steele. The report said the inspector general’s office “has been asking why the FBI continued to cite Steele as a credible source in the renewal applications.”

The New York Times reported in April that the FBI reached out to some of Steele’s foreign sources in an attempt to determine their credibility, and as early as January 2017 agents had concluded that some of the dossier’s contents may have been based upon “rumors and hearsay” which were “passed from source to source.” The agents believed that some of Steele’s information may have even been based upon “Russian disinformation.”

Horowitz, who launched his investigation in 2018, said he would “examine the Justice Department’s and the FBI’s compliance with legal requirements, and with applicable DOJ and FBI policies and procedures, in applications filed with the U.S. Foreign Intelligence Surveillance Court relating to a certain U.S. person [Carter Page]."

Horowitz further stated that he would “review information that was known to the DOJ and the FBI at the time the applications were filed from or about an alleged FBI confidential source [Christopher Steele]. Additionally, the OIG will review the DOJ’s and FBI’s relationship and communications with the alleged source as they relate to the FISC applications.”

Barr has said Horowitz’s investigation should be completed in either May or June.