British ex-spy Christopher Steele declined to give an interview to U.S. Attorney John Durham's team for its review of the Russia investigation.

Representatives for Steele, whose unverified dossier was used by the FBI to obtain warrants to wiretap a member of President Trump's 2016 campaign, were recently approached by members of the federal prosecutor's team, and they said the former MI6 agent would not cooperate with the inquiry, according to Reuters.

Sources for the report said Steele is concerned about politicization and not being treated fairly. Durham's spokesman declined to comment for the report.

Durham, the top federal prosecutor in Connecticut, was appointed last year by Attorney General William Barr to review possible misconduct by federal law enforcement and intelligence officials in the Russia investigation, which Trump called a "witch hunt." The review turned into a criminal investigation in the fall, allowing Durham the power to impanel a grand jury and hand down indictments. Trump gave Barr the “full and complete authority to declassify information” and ordered the intelligence community “to quickly and fully cooperate with the Attorney General’s investigation into surveillance activities during the 2016 presidential election.”

Only one person is publicly known to be under criminal investigation by Durham's team: former FBI lawyer Kevin Clinesmith, who altered a key document in Foreign Intelligence Surveillance Act filings related to onetime Trump campaign adviser Carter Page.

Democrats have criticized the review as a politically motivated scheme to undermine the work of special counsel Robert Mueller and attack Trump's perceived enemies.

Neither Steele’s attorneys nor his private investigative firm, Orbis Business Intelligence, immediately responded to the Washington Examiner’s requests for comment.

In an address to students at Oxford University in England on Friday, Steele said he and Orbis had already "done our duty" by cooperating with the Justice Department watchdog, according to the Daily Beast.

U.S. Attorney John Durham, seen above in 2006, is leading the so-called "investigation into the investigators." (Bob Child/AP Photo)

“We’ve said everything we have to say on the matter," said Steele, who noted this included "confidentiality."

DOJ Inspector General Michael Horowitz conducted an investigation into allegations of FISA abuses and interviewed Steele. His report, released in December, identified at least 17 “significant errors or omissions” in the Justice Department's and the FBI’s use of Steele’s dossier when pursuing FISA warrants to wiretap Page in 2016 and 2017. It revealed that the FBI interviewed Steele's primary Moscow-based source, beginning in January 2017, who "raised significant questions about the reliability of the Steele election reporting."

Steele was hired by opposition research firm Fusion GPS, which was funded by Hillary Clinton's presidential campaign and the Democratic National Committee through the Perkins Coie law firm. Perkins Coie was paid more than $12 million between 2016 and 2017 for its work. Fusion GPS was paid $50,000 per month from Perkins Coie, and Steele was paid roughly $168,000 by Fusion GPS.

“I stand by the integrity of our work, our sources, and what we did," Steele told the students on Friday, adding, “Trump himself doesn’t like intelligence because its ground truth is inconvenient for him.”

Following the release of Horowitz’s report, the Justice Department told the FISA court it believed the final two Page FISA warrants were “not valid."

Steele, who was interviewed by Mueller's investigators, criticized last year's 448-page report that showed the special counsel team did not establish any criminal conspiracy between the Trump campaign and the Kremlin.

Christopher Steele, who compiled an explosive and unproven dossier on President Trump’s purported activities in Russia, is pictured. (Victoria Jones/AP Photo)

“I was surprised that very little of what I had discussed with them appeared in the final report," he said, adding that the final product was "too narrow," and “a number of witnesses — including, for instance, Donald Trump Jr.” dodging interviews “wasn’t great.”

Steele also criticized Horowitz’s report, saying he’d cooperated with the DOJ watchdog for “four to five months” and witnessed “very bad qualities” from some U.S. officials, whom he said acted “in bad faith.”

Durham already interviewed former Adm. Mike Rogers, who retired in 2018 after four years as the National Security Agency’s chief. Rogers was likely consulted because of his experiences uncovering FISA violations and his role in the intelligence community's assessment of Russian interference, where he expressed only “moderate confidence” that Russian President Vladimir Putin actively tried to help Trump’s election chances and harm those of Clinton by contrasting her unfavorably.

The U.S. attorney has also interviewed agents and analysts from the NSA, FBI, and CIA.

Durham is scrutinizing former CIA Director John Brennan about Steele’s dossier, whether it was used in the January 2017 assessment, why former FBI Director James Comey and former FBI Deputy Director Andrew McCabe insisted upon it being part of the assessment, how allegations from the dossier ended up in the assessment's appendix, and whether Brennan had misled about the dossier’s use by the intelligence community.

Barr, whose management of the Justice Department is under review by House Democrats, said in a December interview that Durham’s investigation may be finished by the late spring or summer.

Republicans have cheered on Barr and Durham, hoping they will root out and prosecute "dirty cops" they believe sought to undermine Trump. Georgia Rep. Doug Collins, the ranking member of the House Judiciary Committee, recently told Fox News he believes Durham will not release a report, but rather the public will hear about the progress U.S. attorney has made when there is an indictment. “When he’s ready to charge people, he’ll charge people," Collins said. “And that’s when we’ll know.”