The House Intelligence Committee formally referred Erik Prince, a former informal adviser to President Donald Trump's campaign, to the Justice Department for criminal investigation on Tuesday.

House Intelligence Committee Chairman Adam Schiff asked Attorney General William Barr to investigate whether Prince gave false testimony to the panel in November 2017.

Schiff said the committee identified at least six categories of "materially false" statements Prince made about two meetings: one that took place in the Seychelles in January 2017, and another that took place at Trump Tower in August 2016.

The House Intelligence Committee formally referred Erik Prince, a businessman and informal adviser to President Donald Trump's campaign, to the Justice Department for a criminal investigation on Tuesday.

Prince is the former head of the military contracting firm Blackwater USA, which is now known as Academi. He is also the brother of Betsy DeVos, the Secretary of Education.

In a letter to Attorney General William Barr, House Intelligence Committee Chairman Adam Schiff asked the department to investigate Prince for giving false testimony to the panel when he appeared for a hearing in November 2017 as part of its investigation into Russia's interference in the 2016 US election.

Schiff's office said in a statement that the special counsel Robert Mueller's final report in the FBI's Russia investigation "strongly indicates that Prince's testimony before the Committee was materially false."

The statement said the House panel has identified at least six categories of "materially false" statements Prince made about two meetings:

A January 2017 meeting he had in the Seychelles with Kirill Dmitriev, the head of Russia's sovereign wealth fund and ally of Russian President Vladimir Putin, and George Nader, a Middle East consultant who often represents the governments of UAE and Saudi Arabia

An August 2016 meeting he had with Nader, Donald Trump Jr., and the Israeli social media specialist Joel Zammel at Trump Tower.

Read more: In wild interview, Trump associate Erik Prince acknowledges a 2nd Trump Tower meeting he may have forgotten to disclose under oath

Prince told the committee the January 2017 meeting in the Seychelles was unplanned and that he did not attend as a representative of the incoming Trump administration.

But Mueller's report revealed that shortly before the meeting, Prince met with Nader and the two men discussed Dmitriev. Nader told Prince the Russians were "looking to build a link with the incoming Trump Administration," the report said. Prince agreed to the meeting after.

Prince first acknowledged the August 2016 meeting at Trump Tower in an interview with Al Jazeera's Mehdi Hasan in March.

Hasan initially asked him why he didn't disclose the meeting — first reported by The New York Times in May 2018 — to Congress. Prince replied, "I did. As part of the investigations, I certainly disclosed any meetings. The very, very few I had."

Read more: Trump Organization and Trump family sue Deutsche Bank to prevent it from complying with congressional subpoenas

But a transcript of Prince's testimony shows he did not mention the meeting, and when Hasan pressed him on it, Prince eventually said, "I don't know if they got the transcript wrong. I don't know. I remember — I certainly remember discussing it."

Earlier this month, Schiff told NBC's "Meet The Press" that Prince did not tell the panel about the August 2016 meeting, despite claiming otherwise to Hasan.

Schiff's letter to Barr said Prince's false statements "hindered the Committee's ability to fully understand and examine foreign efforts to undermine our political process and national security, develop appropriate legislative and policy remedies to counter future malign influence operations targeting campaigns and presidential transitions, and inform the American public, as appropriate."

Earlier Tuesday, Schiff told the Washington Post it was unclear whether or not the DOJ will move to prosecute Prince, because it's possible Prince revealed details about the meeting during his proffer sessions with Mueller, which could shield him from criminal charges.

Schiff also told the Post that his committee may ask Steve Bannon — the former head of Breitbart News and former White House chief strategist — to come in for further questioning because he "refused to answer almost all of our questions" when he testified in early 2018.

"When we asked whether he was asserting some privilege, he merely said he was not answering questions because the White House told him not to," Schiff recalled. "The communications between Mr. Prince and Mr. Bannon has apparently fled their devices."