Judiciary Committee Chairman Charles E. Grassley asked the Justice Department Thursday to investigate anti-Trump lawyer Michael Avenatti and his client Julie Swetnick, saying they likely fed senators “materially false” information by accusing Justice Brett M. Kavanaugh of involvement in gang rapes. Mr. Grassley suggested Mr. Avenatti invented clients to try to embarrass Justice Kavanaugh, and the senator said Ms. Swetnick — the only client who did come forward — gave multiple versions of her story. The Iowa Republican, long an advocate for whistleblowers, said he welcomed “well-meaning” complaints from citizens. “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,” he said. Ms. Swetnick, in a sworn statement provided by Mr. Avenatti to the committee, laid out a host of allegations that Justice Kavanaugh and a school chum were complicit in multiple gang rapes of girls during high school parties in the 1980s. In an interview with MSNBC, though, Ms. Swetnick backed off some of those claims and gave a different version of events, saying she only suspected Justice Kavanaugh may have been involved because he was near a punch bowl. Mr. Grassley said in his letter to Attorney General Jeff Sessions and FBI Director Christopher A. Wray that it’s doubtful Ms. Swetnick even knew Justice Kavanaugh, since they went to different schools with different social circles, and Kavanaugh friends came forward to say they didn’t remember ever encountering Ms. Swetnick. “The only apparent commonality between Ms. Swetnick and Judge Kavanaugh is that they both lived in Montgomery County, Maryland in the early 1980s. That is not particularly meaningful for determining whether they knew each other,” the senator wrote. He also dissected Mr. Avenatti’s involvement, saying the lawyer had “a history of claiming to have anonymous clients who never materialize.” And Mr. Grassley recounted Mr. Avenatti’s own lengthy legal entanglements, saying they cast doubt on his credibility. The senator said his committee investigators looked some of them over but stopped because it had become like “beating a dead horse.” “I ask that the FBI investigate whether Mr. Avenatti criminally conspired with Ms. Swetnick to make materially false statements to the committee and obstruct the committee’s investigation,” Mr. Grassley wrote.