Two IRS whistleblowers testifying before the House Oversight Committee on Wednesday have accused the agency of retaliating against them for voicing concerns about how the Department of Justice (DOJ) handled the Hunter Biden tax investigation, according to written versions of their opening statements.

The statements from IRS whistleblowers Gary Shapley and Joseph Ziegler, who spoke publicly for the first time Wednesday, contain allegations of retaliation against them by the agency, with the latter saying he was threatened with “criminal conduct” in response to an email he sent to IRS leadership.

NEW: The U.S. Attorneys who apparently refused to charge Hunter Biden in D.C. and California for alleged tax fraud donated to Joe Biden’s presidential campaign and Kamala Harris’ senate campaign respectively, FEC records show @DailyCaller

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“I ultimately have made the decision to come forward after what I believe were multiple attempts at blowing the whistle internally at the IRS,” Ziegler’s written statement reads.

“My own agency retaliated against me and threatened me with criminal conduct in response to an internal email I sent to IRS leadership, even after years of essentially being left on an island when it came to this investigation.” (RELATED: Here Are The Questions IRS Whistleblowers Must Answer In Front Of Congress)

Ziegler is a gay Democrat who has been with the IRS since 2010 and began working on the Hunter Biden investigation in 2018 as part of his responsibilities with the International Tax and Financial Crimes group, according to his statement. The whistleblower said the DOJ removed his investigative team from the Hunter Biden case and stopped communicating with the team in October 2022.

“I’m pleased to respond to the Committee’s request to assist them in their oversight work. I have a reason to believe that there was gross mismanagement present throughout this investigation, that there was a gross waste of funds relating to the tax dollars spent on investigating this case, and that there was an abuse of authority with DOJ-Tax and the Delaware United States Attorney’s Office,” the statement reads.

Shapley also accused the IRS of retaliating against him after he came forward and testified before the House Ways & Means Committee in late May, his written statement reads. (RELATED: Meet The U.S. Attorney Who Allegedly Covered For Hunter Biden)

“Unfortunately, the senior leaders who are my immediate supervisors are currently making the mistake of retaliating against me for simply reporting outside the chain of command what I genuinely believed was wrong and could not be addressed internally, according to Shapley. “IRS senior leadership is allowing this retaliation and possibly assisting. My direct supervisor has not spoken with me in six weeks. Suddenly, all kinds of unusual scrutiny came down on me and my agents.”

An initiative from Shapley’s IRS group was allegedly “paused” in the wake of his whistleblower testimony, even though IRS and DOJ officials endorsed Shapley’s plan before he testified, according to his statement. Shapley’s statement also mentions how an assistant U.S. attorney speculated about whether his, Shapley’s, initiative was paused as an act of retaliation.

Sworn testimony from Shapley and the other whistleblower raised questions about whether Attorney General Merrick Garland lied under oath regarding political interference in the Hunter Biden case. Shapley testified about a threatening text Hunter Biden allegedly sent to a Chinese business associate and said the Biden-appointed U.S. Attorneys in Washington, D.C., and the Central District of California refused to charge Hunter Biden for alleged tax crimes.

The whistleblowers further testified about how Assistant U.S. Attorney Lesley Wolf led the DOJ’s alleged efforts to shut down attempts to search Hunter Biden’s storage unit in northern Virginia and Joe Biden’s Delaware property where his son had been living.

“I knew that coming forward to share the truth about an investigation into the President’s son would not be easy. I stood to gain nothing, other than to satisfy my conscience,” Shapley’s statement reads. “Making the decision to come forward once allowed me to sleep better, but being slandered and targeted by the government and the Biden family attorneys certainly has not.”

The IRS did not immediately respond to the Daily Caller’s request for comment.

Editor’s note: This story has been updated following the whistleblowers’ statements delivered before Congress on Wednesday.