House Republicans really don’t want to hear from Rudy Giuliani.

Though their impeachment crusade grew out of the former New York City mayor’s anti-Biden machinations, the GOP-led House Oversight Committee spent much of Thursday’s impeachment inquiry hearing voting down repeated efforts by Democrats to subpoena Giuliani and Lev Parnas, his former sidekick.

But Republican attempts to limit what they hear about Giuliani’s activities apparently go further than a few committee votes, according to an FBI whistleblower. In a memo obtained by Mother Jones, Johnathan Buma—an FBI agent who says he conducted foreign influence investigations— alleges that investigators working for House Judiciary Committee Chairman Jim Jordan told him in June that they were not interested in what he knew about Giuliani potentially being “compromised” by Russian intelligence while working as Donald Trump’s personal lawyer.

The memo suggests that Republican investigators privately imposed the same fact-finding limitations Democrats highlighted on Thursday: GOP lawmakers say they want to investigate allegations about Joe Biden, but they appear reluctant to scrutinize the origin of their own probe or turn up details that undermine their preferred narrative. Judiciary Committee staff dispute Buma’s allegations, telling Mother Jones that his account of his interactions with House investigators isn’t accurate. (The Judiciary and Ways and Means Committees are working on the Biden investigation with the House Oversight Committee, which held Thursday’s hearing.)

As Insider, the New Yorker and others have previously reported, Buma—who originally filed a whistleblower complaint with the FBI last year—submitted a statement to the House Judiciary Committee in April 2023. He sent another statement to the Senate Judiciary Committee in July. (Here is Buma’s full statement to the House committee, which recently became public.)

In both statements, the active FBI agent said that his own experience belied claims by GOP lawmakers that the Justice Department obstructed efforts to investigate Hunter Biden while more zealously probing Donald Trump and Trump’s allies. Buma, who says he personally developed leads that helped launch federal probes into Hunter Biden, said his bureau bosses welcomed his Hunter-related information. By contrast, Buma says, his efforts to investigate potential Russian influence over Giuliani were thwarted by FBI higher-ups during both the Trump administration and the Biden administration. The FBI declined to comment on his claims.

Buma, as Mother Jones has reported, said in his July statement that he learned that Pavel Fuks, a wealthy Ukrainian developer who hired Giuliani in 2017, paid Giuliani $300,000, supposedly for security consulting work. But Buma says that the FBI suspected Fuks was a “co-opted asset” of a Russian intelligence service and that his payments were potentially part of an effort to gain influence over Giuliani, who in 2018 became Trump’s personal lawyer.

Fuks denies working for Russia. “Mr. Fuks has never cooperated with Russian intelligence,” a spokesperson says. A Giuliani spokesperson did not respond to questions about Buma’s account.

Giuliani working for a Russian agent would be an obvious security risk. Buma’s allegations are an additional data point, among many, suggesting that America’ Mayor may have been manipulated by Russian agents as he scoured Ukraine for political dirt that could damage Trump’s top rival.

The memo Mother Jones obtained is Buma’s account of his interactions with the House Judiciary Committee’s Republican staff. It details a June 14, 2023, phone call during which Buma made his case to two former FBI agents working for the committee.

Buma writes that after one of the ex-agents referred to the FBI supposedly “slow playing” its Biden probe, “I explained that I was perhaps the first FBI Agent to collect and report information from Ukrainian sources concerning Hunter Biden.” Buma says he told the investigators that his FBI superiors were “happy to receive the information” and that “I never experienced any intelligence suppression when I collected and reported information concerning the Bidens.”

Buma reports that he then described information he received indicating that Giuliani had “collected money from a Ukrainian agent who had been co-opted by the Russian Intelligence Service, Pavlo Fuks…, as well as a group of political operatives located in California, in and around 2020. I said that reporting concerning Giuliani was corroborated extensively by follow up investigations.”

Buma says he told the investigators that “my reporting concerning Giuliani and those surrounding Giuliani was suppressed and my reputation was also blackballed.” That’s when the committee staffers cut him off, according to Buma: “When I tried to explain what was actually going on in Ukraine and where I actually experienced suppression, [the investigators] interjected and said that they were only interested in matters pertaining to Biden.”

A Judiciary committee spokesperson said the staffers involved remembered the phone call differently. “This is not an accurate depiction and misrepresents the Committee’s exchanges with Mr. Buma,” the aide said. “Their discussions with Mr. Buma covered a wide range of topics under the Committee’s purview, including the FBI and Hunter Biden.”

The spokesperson did not specify exactly what the committee disputed. Still, in Buma’s account, committee staffers were explicit: They only wanted to hear about the Bidens. That suggests they didn’t want to consider evidence indicating that a key adviser to Trump might have been compromised by Russian agents. And they didn’t want to deal with the possibility that the president’s lawyer was used to pass along phony claims that helped launch the investigation House Republicans are now pursuing.

Rep. Jamie Raskin, the top Democrat on the Oversight Committee, said at Thursday’s hearing that lawmakers should hear from Giuliani because he an author “of the lie on which this sham impeachment is based.” Republicans clearly contest that, but they don’t seem too interested in the details of how their investigation really got started.