Fusion GPS co-founder Glenn Simpson pleaded the Fifth Amendment before a House Committee on Tuesday, with his attorney accusing GOP lawmakers of McCarthyism.

“This committee would make Sen. Joseph McCarthy proud,” Joshua Levy, Simpson’s attorney, said of the joint investigation by the Judiciary and Oversight committees into potential political bias at the FBI and Justice Department.

He made the remarks shortly after Simpson invoked his constitutional right against self-incrimination as protected under the Fifth Amendment.

Fusion GPS commissioned the so-called Steele dossier that included salacious, unsubstantiated allegations about then-candidate Trump’s ties to Russia. The joint investigation in the House is looking into the Justice Department’s handling of the dossier, as well as action at the FBI that some Republicans say demonstrate bias against Trump.

"This committee has destroyed the reputations and careers of prosecutors and agents. It has gratuitously exposed personal aspects of their private lives. It has levied false accusations of criminal wrongdoing against them,” Levy said. “And this mistreatment is no different as applied to our client Mr. Simpson.”

Rep. Mark Meadows Mark Randall MeadowsAnxious Democrats amp up pressure for vote on COVID-19 aid Pelosi hopeful COVID-19 relief talks resume 'soon' The Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November MORE (R-N.C.) later told reporters that Levy was grandstanding.

"Mr. Levy is looking for a moment on all the networks so that he can have a viral moment attacking the credibility of an investigation,” Meadows said. “It was his client that refused to answer today. It was his client that has made a number of assertions that, quite frankly, are not being supported by the facts.”

Meadows, head of the ultra-conservative Freedom Caucus, raised questions about the legality of Simpson pleading the Fifth before a congressional committee.

“It has to be a concern that you have a reasonable apprehension of criminal prosecution in order to invoke it, and in that you can't just invoke the Fifth in order to avoid questions before Congress,” the North Carolina Republican said, noting that the committee would consider their options how to proceed regarding Simpson over the “next 24 hours.”

Later this week the committee is slated to hear from other individuals tied to the Steele dossier, including former FBI counsel James Baker and Nellie Ohr, whose husband Bruce Ohr, worked as a top official at the Justice Department during the 2016 election.

Levy refused to answer questions on the validity of the dossier.

“The Russians tried to elect Donald Trump president,” Levy said. “It's been proven. And you're quibbling about whether this little detail on page 127 was correct or not? It's absurd, we gotta stop this.”

Meadows pointed out that the details contained in the dossier are key to the question of whether President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE or members of his campaign “colluded” with Russia to win the 2016 election.

“There are a number of us who believe that Russian interference actually happened in the election – the difference is what has been alleged is that there was collusion, and there's been no evidence of collusion,” Meadows said. “And that's where the dossier has its foundation, is on the collusion narrative, and there is zero evidence to support that.”

Levy said four individuals named in the dossier were found guilty of criminal action -- “have either pleaded guilty in a criminal charge or have been indicted/convicted of criminal charges.”

Meadows shot back that at least one of those individuals, former Trump campaign chairman Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE, was convicted of crimes committed before the dossier was even created.

“There have been more people that have not been convicted, if you're talking about Paul Manafort … it wasn't for the purposes which the dossier was written, which was a collusion narrative,” Meadows said. “He was actually convicted on charges that predated Mr. Simpson's involvement in the dossier in his investigation.”