Rep. Devin Nunes Devin Gerald NunesSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Sunday shows preview: With less than two months to go, race for the White House heats up Sunday shows preview: Republicans gear up for national convention, USPS debate continues in Washington MORE (R-Calif.) lashed out at Intelligence Committee Chairman Adam Schiff Adam Bennett SchiffChris Matthews ripped for complimenting Trump's 'true presidential behavior' on Ginsburg Trump casts doubt on Ginsburg statement, wonders if it was written by Schiff, Pelosi or Schumer Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence MORE (D-Calif.) on Friday for meeting with Glenn Simpson, the co-founder of Fusion GPS, an opposition research firm that has become embroiled in the ongoing national debate about Russian efforts to intervene in the 2016 presidential election.

In an interview with Hill.TV's Buck Sexton, Nunes, the ranking Republican on Intelligence who served as the panel's chairman in the last Congress, denounced the Simpson-Schiff encounter as "very troubling," adding that the Fusion GPS executive "is at the center of our investigation" due to his connections with figures who have been involved in government investigations.

Nunes said these figures include Kremlin-connected attorney Natalia Veselnitskaya and Christopher Steele, the author of a report which claimed that future president Donald Trump was substantially compromised by the Russian government.

Simpson has testified before both House and Senate intelligence committees. During his appearance before the House body, he mostly invoked his Fifth Amendment rights not to answer questions.

"What was talked about the meeting? Glenn Simpson is a central figure in all of this. He is the man behind the dossier," Nunes said.

The California Republican added that he wanted to bring Simpson back before the House intelligence panel. Now that Democrats control the committee, however, it is unclear when that may happen.

The Simpson-Schiff encounter, which took place at a security conference in July of last year, was disclosed in an opinion piece by Hill.TV's John Solomon on Thursday.

Simpson's company as well as Schiff have said that the meeting was not pre-planned, that they did not discuss anything of substance, and that the two men have not been in contact since.

Speaking to Sexton, Nunes accused Schiff of having met with Simpson on earlier occasions.

"The fact that they're coordinating doesn't really surprise me because Glenn Simpson is a Democratic operative working for the Democratic Party," Nunes said.

"So the fact that he's meeting with Democrats on Capitol Hill is not a surprise. That's his business. That's what he does. There just is a little bit of surprise that people haven't taken it serious that this guy needs to be investigated. And clearly they weren't, if they were meeting and having conversations in 2018. My guess is that they were having conversations before that."

On Wednesday, Schiff announced that the newly empowered Democratic majority on the intelligence committee would be re-opening the panel's Trump-Russia investigation which Nunes and the former GOP majority had ended in March of 2018.

Schiff has previously criticized Nunes for not doing more to investigate Trump. Democrats have long argued that Nunes was more interested in protecting Trump than in investigating him while he served as the Intelligence chairman.

“During the prior Congress, the Committee began to pursue credible reports of money laundering and financial compromise related to the business interests of President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE, his family, and his associates,” Schiff said in a statement. "Unfortunately, these and numerous other avenues of inquiry were not completed during the last Congress."

A similar investigation has been operating continuously in the Senate intelligence committee.

On Thursday, Sen. Richard Burr Richard Mauze BurrRep. Mark Walker says he's been contacted about Liberty University vacancy Overnight Defense: Trump rejects major cut to military health care | Senate report says Trump campaign's Russia contacts posed 'grave' threat Senate report describes closer ties between 2016 Trump campaign, Russia MORE, the chairman of the panel, once again said that he and other members had not found evidence that Trump campaign officials had "colluded" with Russia during the president's former campaign.

The congressional Trump-Russia probes have been operating in tandem with a much broader inquiry being run by Department of Justice 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 which has obtained a number of convictions and guilty pleas from people who worked with the president's 2016 operation, including his former 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.

Mueller is currently trying a legal case against Roger Stone Roger Jason StoneOur Constitution is under attack by Attorney General William Barr Justice IG investigating Stone sentencing: report Romney says Trump's protest tweets 'clearly intended to further inflame racial tensions' MORE, a long-time Trump friend, whom the specially prosecutor has accused of lying about attempts to obtain information from the leader of a website that published stolen emails from the president's former Democratic rival, Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE. Stone firmly denies all charges.

Trump lashed out at Schiff on Twitter on Friday for meeting with Simpson, and also for hiring former White House intelligence staffers for his investigation.

— Matthew Sheffield