EXCLUSIVE: Sen. Ron Johnson, R-Wis., is demanding the Department of Justice open an internal investigation or appoint a special counsel, following new whistleblower allegations that the DOJ and FBI illegally suppressed information on Hunter Biden and that the FBI was "weaponized" against sitting members of the Senate.

The Wisconsin senator's demands come the day after Sen. Chuck Grassley, R-Iowa, revealed that new "highly credible whistleblowers" at the DOJ and FBI shared information with his office detailing a "pattern of active public partisanship" at the agencies pertaining to investigations into the Trump campaign and suppression of information on the Hunter Biden probe.

Johnson, who serves as the ranking member on the Senate Permanent Subcommittee on Investigations, wrote a follow-up letter Tuesday to Attorney General Merrick Garland, FBI Director Chris Wray, Director of National Intelligence Avril Haines and DOJ Inspector General Michael Horowitz. 

In the letter, he says the new whistleblower information confirms there was a "scheme" in place among FBI officials to discount derogatory information about the president's son Hunter Biden by labeling it as "disinformation."

GRASSLEY PRESSES DOJ, FBI FOR TRANSPARENCY ON 'PARTISAN' POLITICIZATION OF AGENCIES, HUNTER BIDEN PROBE

Hunter Biden's laptop was confirmed by NBC News on May 19

NBC News authenticated the contents of Hunter Biden's laptop on May 19.  (BRENDAN SMIALOWSKI/AFP via Getty Images)

Both Johnson and Grassley recounted events between July and October 2020, during which the FBI, including Assistant Special Agent in Charge Timothy Thibault, FBI Supervisory Intelligence Analyst Brian Auten and Democratic senators, gave Republicans investigating the Hunter allegations the runaround on information, falsely alleging that the GOP was advancing "foreign disinformation" regarding the now-president's son.

An Aug. 6, 2020 meeting, GOP senators now allege after whistleblower corroboration, was explicitly intended to "undermine" their investigation into Hunter Biden.

"If these recent whistleblower revelations are true, it would strongly suggest that the FBI’s August 6, 2020 briefing was indeed a targeted effort to intentionally undermine a Congressional investigation," Johnson wrote in the Tuesday letter. "The FBI being weaponized against two sitting chairmen of U.S. Senate committees with constitutional oversight responsibilities would be one of the greatest episodes of Executive Branch corruption in American history," Johnson continues.

"For nearly two years I have sought to get information from the FBI and the Office of the Director of National Intelligence (ODNI) about the purpose of, and who ordered, this briefing. On May 3, 2021, Senator Grassley and I reiterated these requests in a letter to Directors Wray and Haines. Both failed to provide complete responses," Johnson stated.

Hunter Biden Joe Biden

Hunter Biden's ex-wife detailed how she heard about the affair between Biden and his brother's widow Hallie in her new memoir.  (REUTERS/Joshua Roberts)

The senator stated that the FBI's integrity is now being called into question and the agency can "no longer be trusted to investigate Hunter Biden with integrity and the equal application of law." Additionally, he states that Garland has failed to provide both Grassley and him "assurances" that the DOJ probe will be free from conflicts of interest.

"The Office of the Inspector General (OIG) may be able to provide an objective review of this matter, but it has not been forthcoming to Senator Grassley or me. If the OIG is unwilling or unable to conduct an investigation into the potential political targeting of U.S. Senators by federal law enforcement entities, then the appointment of a Special Counsel would be fully justified and long overdue," concluded Johnson.

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Grassley wrote Monday to the FBI and DOJ, stating that the new whistleblower information provided to his office "involves concerns about the FBI's receipt and use of derogatory information related to Hunter Biden, and the FBI's false portrayal of acquired evidence as disinformation."

Sen. Ron Johnson of Wisconsin

Sen. Ron Johnson (R-WI) arrives to a news conference with Republican senators to discuss the origins of COVID-19 on June 10, 2021 in Washington, DC.  (Anna Moneymaker/Getty Images)

"In light of these allegations, I remain very concerned that political bias by a select group of Justice department and FBI officials has infected the Justice Department and FBI's usual process and procedure to open and pursue high-profile and politically charged investigations," Grassley wrote, demanding further explanation from the agencies.

The federal investigation into the first son's tax affairs has reached a "critical stage," a source told Fox News last week. Officials are looking into whether to charge President Biden's son with various tax violations, possible foreign lobbying violations and more.

A separate source told Fox News that the federal grand jury looking into Hunter Biden’s business dealings wrapped up its latest term late last month but said no charges have been filed.

The DOJ confirmed receipt of the letter but did not comment beyond that.

FBI and ODNI did not immediately respond to a request for comment.