A top Senate Republican is being cut out from a congressional investigation into IRS whistleblower claims that a Justice Department and IRS probe of Hunter Biden's alleged tax fraud is being mishandled. 

Sen. Chuck Grassley, R-Iowa, who is a member of the Senate Finance Committee and co-chairman of the Whistleblower Protection Caucus, is being denied access to the investigation by committee chairman Sen. Ron Wyden, an Oregon Democrat.

Specifically, Grassley and his investigative team are being denied access to an interview scheduled to take place in the coming weeks with one of the whistleblowers who alleges that the whistleblower's entire team had been removed last week from the Hunter Biden probe as retaliation for coming forward with claims the probe was being mishandled.

A spokesperson for Grassley said the IRS whistleblower’s attorneys "have specifically included Sen. Grassley in their communications with Congress, so there’s no legitimate reason to exclude Grassley’s staff from participating in this investigation."

Hunter Biden, right with President Biden leaving Air Force One

President Biden and his son, Hunter Biden, step off Air Force One, Feb. 4, 2023, at Hancock Field Air National Guard Base in Syracuse, New York. (AP Photo/Patrick Semansky)

IRS WHISTLEBLOWER LETTER ACCUSES DOJ OF RETALIATION IN HUNTER BIDEN PROBE

"Sen. Grassley and his investigations unit are subject-matter experts on both whistleblower protections and the Biden family business controversies. They also happen to be very familiar with the specific statutes protecting sensitive tax information," Taylor Foy, communications director for Grassley, told Fox News Digital.

An IRS criminal supervisory agent first came forward to seek whistleblower protection in an April 19 letter to Congress, claiming that the investigation into Hunter Biden is being mishandled by the Biden administration.

Sen. Chuck Grassley

Sen. Chuck Grassley, R-Iowa (Olivier Douliery/AFP via Getty Images)

HUNTER BIDEN INVESTIGATION BEING MISHANDLED, 'CLEAR CONFLICTS OF INTEREST': IRS WHISTLEBLOWER

The whistleblower's attorney, Mark D. Lytle of the Washington, D.C.-based law firm Nixon Peabody LLP, tells members of the House of Representatives and Senate that his client has been overseeing the "ongoing and sensitive investigation of a high-profile, controversial subject since early 2020 and would like to make protected whistleblower disclosures to Congress."

Hunter Biden

Hunter Biden (Getty Images)

IRS WHISTLEBLOWERS CLAIM RETALIATION IN CONNECTION TO HUNTER BIDEN COMPLAINT

Lytle also said his client has information that the investigator failed to mitigate "clear conflicts of interest," adding that the investigator allegedly allowed preferential treatment and politics to infect decisions and protocols normally followed by law enforcement professionals if the subject was not politically connected.

Last week, the IRS removed the "entire investigative team" from its multiyear tax fraud investigation into Hunter Biden, which the whistleblower said was "clearly retaliatory," according to a Monday report.

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"Today the Internal Revenue Service (IRS) Criminal Supervisory Special Agent we represent was informed that he and his entire investigative team are being removed from the ongoing and sensitive investigation of the high-profile, controversial subject about which our client sought to make whistleblower disclosures to Congress," reads a letter from a whistleblower's lawyer that was sent to the House and Senate judiciary committees last week.