House Intelligence Committee ranking member Rep. Devin Nunes, R-Calif., told committee chairman Rep. Adam Schiff, D-Calif., that he is "in need of rehabilitation" after a Justice Department Inspector General report on the FBI's Russia investigation and its use of the Foreign Intelligence Surveillance Act (FISA) contradicted Schiff's past assertions.

In a 2018 memo, Schiff dismissed Nunes' concerns about the FBI's use of a FISA warrant to monitor former Trump campaign adviser Carter Page. The IG report confirmed that the FBI's warrant applications included 17 "significant errors and omissions," including a doctored email and reliance on unverified information from British ex-spy Christopher Steele.

COMEY ADMITS ERROR IN DEFENSE OF FBI'S FISA PROCESS AFTER IG REPORT: 'I WAS WRONG'

"After publishing false conclusions of such enormity on a topic directly within this committee's oversight responsibilities, it is clear you are in need of rehabilitation, and I hope this letter will serve as the first step in that vital process," Nunes said in a Sunday letter.

Schiff's memo downplayed Steele's role and denied FBI wrongdoing, saying, "FBI and DOJ officials did not 'abuse' the Foreign Intelligence Surveillance Act (FISA) process, omit material information, or subvert this vital tool to spy on the Trump campaign." Schiff also claimed at the time that the DOJ "made only narrow use of information from Steele's sources" for the Page warrant.

Nunes listed these statements and others, such as how the FBI conducted a "rigorous process" when vetting Steele's information, noting that "[t]he IG report exposed all these declarations as false."

IG Michael Horowitz's report indicated that Steele's information was not properly vetted, yet was key in convincing attorneys to give the go-ahead to the FISA warrant application, which was previously deemed a "close call."

READ: DOJ IG HOROWITZ STATEMENT TO SENATE JUDICIARY COMMITTEE ON RUSSIA PROBE REPORT

Nunes recognized Schiff's acknowledgment of the "issues and errors" described in Horowitz's report, but said that his opposition to concerns raised by Attorney General Bill Barr and Connecticut U.S. Attorney John Durham -- who is conducting a broader probe of the Russia investigation's origins -- "makes it clear your rehabilitation will be a long, arduous process."

Nunes cited Schiff's failure to use his committee to conduct proper oversight while using it "as a launching pad to impeach the president for issues that have no intelligence component at all." He accused him of "hijacking" the committee, claiming, "As part of your rehabilitation, it's crucial that you admit you have a problem."

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Schiff's office did not immediately respond to Fox News' request for comment about the letter, but in an interview with "Fox News Sunday," Schiff acknowledged the FBI's issues as described in Horowitz's report, and claimed he "would have called out the FBI" had he known of them.

The GOP ranking member called on the Democratic chairman to call Horowitz before their committee "at the nearest opportunity." Horowitz has already appeared before the Senate Judiciary Committee, and is scheduled for another hearing before the Senate Homeland Security Committee.

Fox News' Brooke Singman contributed to this report.