The co-founder of opposition research firm Fusion GPS Glenn Simpson pleaded the Fifth Amendment on Tuesday to House Republicans who were seeking his testimony on the role his company played in creating an investigation into Donald Trump's presidential campaign.

“Mr. Simpson has proudly stood today on his constitutional privileges not to testify,” Simpson’s lawyer, Joshua Levy, told reporters Tuesday after his client asserted his constitutional right against self-incrimination.

"The House Judiciary Committee has subpoenaed Mr. Simpson to appear today for testimony, and this committee has shown no interest that Russia interfered in the 2016 election," Levy added. He said the committee has "destroyed the reputation and careers of prosecutors and agents."

Fusion GPS compiled a dossier that claimed to connect Russia to Trump. The company hired Christopher Steele to write it after Democrats agreed to pay for it.
[More: Fusion GPS co-founder rejects House Judiciary Committee subpoena]

Though it was salacious and largely unverified, the dossier eventually made its way to the FBI, and Republicans have alleged that information was misused to open the federal government’s Russia investigation.

Simpson has also come under fire for his relationship with Bruce Ohr, a Justice Department lawyer. He had an usually close relationship with Ohr, who brought some of the dossier information to the Justice Department and FBI. Ohr’s wife, Nellie Ohr, was contracted by Fusion GPS.

Nellie Ohr is expected before the House Judiciary and Oversight Committees on Friday, and former FBI lawyer James Baker is also scheduled to give a deposition behind closed doors on Thursday.

House Republicans have zeroed in on the dossier and what top Justice Department and FBI officials did with it during the investigations into Russian election interference and possible connections to the Trump campaign.

President Trump has constantly echoed those concerns, tweeting as recently as Tuesday morning about Simpson and Bruce and Nellie Ohr.

“Is it really possible that Bruce Ohr, whose wife Nellie was paid by Simpson and GPS Fusion for work done on the Fake Dossier, and who was used as a Pawn in this whole SCAM (WITCH HUNT), is still working for the Department of Justice????? Can this really be so?????” he tweeted.

Trump also noted that Simpson pleaded the Fifth in a separate tweet, and asked, “Where is [Attorney General] Jeff Sessions?”

Trump has berated Sessions for recusing himself from the Justice Department’s Russia investigation, which paved the way for the appointment of special counsel Robert Mueller.

Rep. Mark Meadows, R-N.C., told reporters that they are looking at next steps following Simpson’s non-answers, which include holding him in contempt.

Meadows said those conversations with Reps. Bob Goodlatte and Trey Gowdy, chairmen of the two committees, are "ongoing” and something will be decided in the “coming days.”

“Simpson has to have a reasonable apprehension of criminal prosecution in order to validly invoke the Fifth,” said Meadows, “But if not, you cannot just invoke the Fifth to avoid answering congressional questions.”

Goodlatte, R-Va., called Simpson’s non-deposition “disappointing.”

“Today we expected Mr. Simpson to answer questions that have not been explored by other congressional committees to help advance our joint investigation. Instead, Mr. Simpson has refused to cooperate with our investigative team and has denied the American people answers to important questions,” said Goodlatte in a statement — but made no mention of holding Simpson in contempt.