By Ariane de Vogue and Manu Raju, CNN

(CNN) -- Senate Judiciary Chairman Chuck Grassley on Thursday referred Julie Swetnick and her lawyer Michael Avenatti to the Department of Justice for a possible criminal investigation over allegations they made false statements to Congress about now-Supreme Court Justice Brett Kavanaugh.

"I am writing to refer Mr. Michael Avenatti and Ms. Julie Swetnick for investigation," Grassley wrote in a letter to Attorney General Jeff Sessions and FBI Director Christopher A. Wray, for potential "materially false statements they made to the Committee during the course of the Committee's investigation. "

In a statement, Grassley said, "When a well-meaning citizen comes forward with information relevant to the committee's work, I take it seriously. It takes courage to come forward, especially with allegations of sexual misconduct or personal trauma. I'm grateful for those who find that courage."

Grassley continued, "But in the heat of partisan moments, some do try to knowingly mislead the committee. That's unfair to my colleagues, the nominees and others providing information who are seeking the truth."

Avenatti, a potential 2020 Democratic presidential candidate, told CNN that the referral is "completely baseless and political."

"I look forward to a thorough investigation into Judge Kavanaugh," Avenatti said. "We have all waited long enough."

Avenatti also tweeted criticism aimed at the Iowa Republican senator.

"It is ironic that Senator Grassley now is interested in investigations," Avenatti wrote. "He didn't care when it came to putting a man on the SCOTUS for life. We welcome the investigation as now we can finally get to the bottom of Judge Kavanaugh's lies and conduct. Let the truth be known."

Swetnick's statement, which was submitted to the committee last month, alleges that Kavanaugh and his friend Mark Judge were present at a party where Swetnick was drugged and "gang raped." In the statement, Swetnick did not identify either man as her attacker in the incident. Both men categorically denied the allegations.

In the 12-page letter, Grassley said that Swetnick's allegations "materially affected" the committee's investigation and that Kavanaugh "under penalty of a felony" categorically denied the allegations.

Grassley said that Swetnick had contradicted her own allegations in an interview with NBC, and that the committee spoke with "45 individuals, obtained 25 written statements and reviewed numerous other materials" but could not find "any information to corroborate Ms. Swetnick's claims."

"I ask that the FBI investigate whether Mr. Avenatti criminally conspired with Ms. Swetnick to make materially false statements to the Committee," Grassley wrote.

Kavanaugh's attorney, Beth Wilkinson, told CNN's Wolf Blitzer when the allegations arose that her client never met Swetnick.

"He has never met this woman, he doesn't know Ms. Swetnick, he didn't go to parties with her," Wilkinson said.

Wilkinson said that she had received calls from women and men who went to high school with him and they also didn't remember Swetnick.

According to the declaration, Swetnick said that if she were ever "called to testify" about the statements in the declaration she would do so.

On September 29, Grassley referred charges to the Department of Justice and the FBI regarding another person who contacted Sen. Sheldon Whitehouse and his committee staff reporting an allegation of sexual misconduct by Kavanaugh.

This story has been updated.