In this Oct. 8, 2018, file photo, Supreme Court Justice Brett Kavanaugh stands before a ceremonial swearing-in in the East Room of the White House in Washington. Credit: Susan Walsh | AP

WASHINGTON — A Democratic senator told the FBI last fall of a new allegation of sexual impropriety against then-Supreme Court nominee Brett Kavanaugh — a claim that was not investigated at the time but has since become public in an upcoming book chronicling the bitter confirmation fight.

Sen. Christopher Coons, D-Delaware, wrote to FBI Director Christopher Wray on Oct. 2, 2018, requesting an “appropriate follow up” with one individual who had come to Coons with information about Kavanaugh. Although the person’s name was redacted in the one-page letter, a spokesman for Coons confirmed Monday that the individual was Max Stier, a classmate of Kavanaugh’s at Yale University who now leads a prominent nonpartisan group in Washington.

In the letter obtained by The Washington Post, Coons said “several individuals” who wanted to share information with federal authorities had contacted his office, but they had had “difficulty reaching anyone who will collect their information.”

“I cannot speak to the relevance or veracity of the information that many of these individuals seek to provide, and I have encouraged them to use the FBI tip portal or contact a regional FBI field office,” Coons wrote to Wray. But the Stier allegation, Coons said, “was one individual whom I would like to specifically refer to you for appropriate follow up.”

The two top senators on the Judiciary Committee at the time — Sens. Charles Grassley, R-Iowa, its chairman, and Dianne Feinstein, D-California — were copied on Coons’ letter to the FBI.

Aides said Coons wrote the letter because he wanted to get relevant information about credible allegations as quickly as possible to the FBI. When Coons wrote the letter Oct. 2, FBI officials were in the middle of conducting a new, supplemental background check on Kavanaugh — facing multiple allegations of sexual misconduct — ahead of his confirmation vote. Kavanaugh was confirmed Oct. 6.

Stier had also requested to remain confidential, aides said, so Coons wanted to send the information directly to the FBI so sensitive details would not become public.

The new allegation against Kavanaugh was made public Saturday night in a New York Times report — which was an excerpt from a forthcoming book about the justice from two of its reporters. Stier, a Yale classmate, said he saw Kavanaugh with his pants down at a party, where friends pushed Kavanaugh’s penis into the young woman’s hand, according to the Times.

According to the book, “The Education of Brett M. Kavanaugh,” the woman involved in the alleged incident has told friends she does not recall it.

The Washington Post last year confirmed that two intermediaries had relayed such a claim to lawmakers and the FBI. The Post did not publish a story in part because the intermediaries declined to identify the alleged witness and because the woman who was said to be involved declined to comment.

As the FBI was wrapping up its investigation, the intermediaries working on behalf of Stier delivered his account to agency officials. The intermediaries told The Post last year they had relayed that a classmate of Kavanaugh had witnessed the incident while taking a study break at Yale’s Lawrance Hall. They declined to give The Post the classmate’s name.

Stier was one of several people who went to Yale at the same time as Kavanaugh who reached out to the FBI last year seeking to provide information, but they were not interviewed, according to people familiar with the matter.

Washington Post writer Devlin Barrett contributed to this report.