Fox News’ own research team has warned colleagues not to trust some of the network’s top commentators’ claims about Ukraine.

An internal Fox News research briefing book obtained by The Daily Beast openly questions Fox News contributor John Solomon’s credibility, accusing him of playing an “indispensable role” in a Ukrainian “disinformation campaign.”

The document also accuses frequent Fox News guest Rudy Giuliani of amplifying disinformation, as part of an effort to oust former U.S. Ambassador to Ukraine Marie Yovanovitch, and blasts Fox News guests Victoria Toensing and Joe diGenova—both ardent Trump boosters—for “spreading disinformation.”

The 162-page document, entitled “Ukraine, Disinformation, & the Trump Administration,” was created by Fox News senior political affairs specialist Bryan S. Murphy, who produces research from what is known as the network’s Brain Room—a newsroom division of researchers who provide information, data, and topic guides for the network’s programming.

The research brief is especially critical of Solomon, a former opinion columnist at The Hill whose opinion pieces about Ukraine made unsubstantiated claims about its government interfering in the 2016 U.S. presidential election. Solomon’s pieces for The Hill fueled Giuliani’s efforts to dig up dirt in Ukraine, which eventually helped lead to President Donald Trump’s impeachment. Trump has also frequently cited Solomon’s questionable reporting on Twitter in his own defense.

While Solomon is portrayed on Sean Hannity’s show as a crusading “investigative reporter”—despite The Hill overtly branding him an opinion columnist—the Brain Room document accuses the contributor of taking part in a Ukrainian smear campaign. “John Solomon played an indispensable role in the collection and domestic publication of elements of this disinformation campaign,” the Fox briefing book notes.

Those smears, according to the briefing, were driven by people like disgraced former Ukrainian prosecutor Yuriy Lutsenko and the allies of Dmytro Firtash, an indicted Ukrainian oligarch and accused high-level Russian mafia associate (an accusation he denies). Both Lutsenko and Firtash have been seen as forces driving Giuliani’s efforts in Ukraine to dig up dirt on Trump’s political enemies.

Elsewhere in the internal brief, Murphy urges Fox News employees to focus on a wide range of alleged journalistic misdeeds from Solomon, including ”non-disclosure of conflicts, use of unreliable sources, publishing false and misleading stories, misrepresentation of sources, and opaque coordination with involved parties.”

Despite Solomon’s reputation for questionable claims, he continued to be a fixture on Fox News even as impeachment inquiry witness Lt. Col. Alexander Vindman—who listened in on the infamous quid pro quo call between Trump and Ukraine’s president—testified that “all the elements” of the columnist’s supposed Ukraine reporting were “false.” The Hill announced it would conduct a full review of Solomon’s work. Though he has not appeared on Hannity’s show since Dec. 26, Solomon’s most recent Fox appearance came last Friday on Laura Ingraham’s primetime show.

The existence of the briefing book was first publicly flagged by Marcus DiPaola, a former freelance Fox News producer. Solomon, who years ago wrote for Newsweek/The Daily Beast, did not respond to a request for comment. Nor did Giuliani, Toensing, and diGenova.

“The research division of FOX News produces a briefing book for all major stories, which serves as a standing collection of extensive data on major topics for internal use by all those in editorial functions. The Ukraine briefing book is nothing more than a comprehensive chronological account of what every person involved in the Ukraine controversy was doing at any identifiable point in time, including tracking media appearances of major players who appeared on FOX News and in many other outlets,” Mitch Kweit, senior vice president of the Brain Room, said in a statement to The Daily Beast. “The 200 page document has thousands of data points and the vast majority have no relation to FOX News—instead it’s now being taken out of context and politicized to damage the network.”

The document also disputes the credibility of Trump personal attorney and frequent Fox News guest Rudy Giuliani. While the former New York mayor has regularly appeared on Fox to justify his efforts to pressure the Ukrainian government to investigate former Vice President Joe Biden’s son Hunter on Trump’s behalf, Murphy claims Giuliani is easily fooled by Ukrainian disinformation.

Murphy writes that Giuliani has a “high susceptibility to disinformation” disseminated by Ukrainians like Lutsenko and Firtash. The document notes that two indicted Giuliani pals, Lev Parnas and Igor Fruman, had “strong reported financial links to Firtash.”

“Reading the timeline in its entirety—not a small task—makes clear the extensive role played by Rudy Giuliani and his associates, Lev Parnas and Igor Fruman, in spreading disinformation,” Murphy writes.

The brief also questions the credibility of diGenova and Toensing, a married pair of Washington lawyers and frequent Fox News guests who appeared across the network’s right-wing commentary shows.

The pair were regularly deployed by Fox hosts like Hannity, Lou Dobbs, and Tucker Carlson to criticize the Democrats’ impeachment inquiry and attack Fox News analysts who questioned the president’s actions. DiGenova briefly stopped appearing on Fox after spewing on-air the anti-Semitic trope that liberal billionaire George Soros “controls” the U.S. State Department. And then he and his wife have altogether ceased appearing on the network since December.

Fox News itself reported in September that diGenova and Toensing were working with Giuliani to dig up dirt on the Bidens. “Notable are the roles of Joe diGenova and Victoria Toensing in spreading disinformation and their parroting of beneficial narratives while employed by Firtash,” the internal research brief adds.

During their Fox appearances about the unfolding Ukraine scandal in 2019, diGenova and Toensing failed to note that they were working for Firtash, who is attempting to avoid extradition to the United States. The pair had billed the Ukrainian oligarch $1 million as of October, according to a Bloomberg report.

Last year’s document urges Fox employees to consider diGenova and Toensing’s failure to note during their Fox appearances that they were employed by Firtash. It advises employees to focus on the pair’s “non-disclosure of financial motives and representation of Firtash while spreading false and misleading stories.”

The briefing book is also seemingly critical of Fox’s own coverage, urging employees to note the role that unnamed “US Media” outlets played a role in the “amplification of disinformation stories from clearly unreliable sources and non-disclosure of conflicts by guests.” While Fox isn’t specifically named in the introduction, much of the timeline focuses on appearances made on Fox programs, and Murphy writes that the “most prominent” outlets who amplified the disinformation campaign are mentioned in the timeline—a possible reference to Fox News itself.

The document notes omissions by Hannity, who frequently had Solomon, Toensing, diGenova, and Giuliani on his show. Murphy notes that the primetime star continued to refer to Solomon as an “investigative reporter” even after The Hill explicitly labeled his work to be “opinion.” The briefing also dings Hannity for failing to mention, in a segment featuring Toensing and diGenova about an affidavit filed on behalf of Firtash, that the pair were working for the Ukrainian oligarch Firtash—an obvious conflict of interest.

“At no time during the program does Hannity, Toensing, and diGenova mention who requested the statement nor do they discuss that they are Firtash’s attorneys,” the briefing book reads.

—With additional reporting by Justin Baragona.