The head of the House Judiciary Committee is preparing to subpoena Glenn Simpson, co-founder of the opposition research firm that helped compile the controversial dossier.

House Judiciary Chairman Bob Goodlatte Robert (Bob) William GoodlatteNo documents? Hoping for legalization? Be wary of Joe Biden Press: Trump's final presidential pardon: himself USCIS chief Cuccinelli blames Paul Ryan for immigration inaction MORE (R-Va.) is readying the order after Joshua Levy, a lawyer representing the Fusion GPS co-founder, wrote a scathing letter accusing GOP lawmakers of leading an investigation in which they "flout rules of confidentiality in order to manipulate the record and prejudice witnesses."

"The chairman does intend to subpoena him," a Republican House Judiciary Committee aide told The Hill after the letter surfaced on Thursday.

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In a letter to Goodlatte and House Oversight Chairman Trey Gowdy Harold (Trey) Watson GowdySunday shows preview: Election integrity dominates as Nov. 3 nears Tim Scott invokes Breonna Taylor, George Floyd in Trump convention speech Sunday shows preview: Republicans gear up for national convention, USPS debate continues in Washington MORE (R-S.C.), Levy not only rejected the House lawmakers request to interview Simpson, he also accused them of trying to silence whistleblowers.

"Part and parcel of this concerted effort by the President’s congressional allies has been a campaign of retaliation against the government’s whistleblowers, including our client Mr. Simpson, for their willingness to cooperate with US law enforcement and for their exercise of their constitutional rights to free speech and political activity as American citizens," Levy wrote.

Levy also said the joint investigation was wasting tax payer money as Republican lawmakers worked to undermine special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's investigation into ties between the Trump campaign and Russia.

"The so-called 'task force,' formed by members of the two committees you chair, has demonstrated a propensity to flout rules of confidentiality in order to manipulate the record and prejudice witnesses," he wrote in part.

"The 'task force' is comprised of some of the President’s staunchest protectors, who have misspent American taxpayers’ dollars to undermine the Special Counsel’s investigation into Russia’s interference in the 2016 election, even after the U.S. Intelligence Community and the U.S. Senate Select Committee on Intelligence both confirmed that the Russian government interfered in the 2016 presidential election for the purpose of electing Donald J. Trump," he added.

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President Trump Simpson has faced GOP scrutiny for his involvement in compiling the controversial dossier that makes a series of salacious and unverified allegations about, and possible ties between his campaign and Russia.

Simpson has already met with the House and Senate intelligence committees.

Republicans have alleged that a contractor working for his firm, Nellie Ohr, could have passed the dossier on to her husband Bruce Ohr, who worked as a top official with the Department of Justice during the election.

A lawyer on Hillary Clinton’s presidential campaign is believed to have retained Fusion GPS during the election to dig up dirt on Trump, then the Republican presidential contender.

Simpson had hired former British spy Christopher Steele to help compile the memos about Trump’s ties to Russia.

Simpson is one of several involved in the dossier that House GOP lawmakers want to speak to.

Congressional investigators are expected to interview Nellie Ohr next month.