A former classmate at Yale University saw Mr Kavanaugh’s penis being pushed into the hand of a female student at a drunken dorm party, according to the New York Times.
The witness account – which has not previously been made public – appears to echo allegations made by Deborah Ramirez, one of three women who came forward after the judge was nominated by Donald Trump.
Her legal team gave the FBI a list of more than 25 people who may be able to corroborate her story, but none of them were interviewed and she was never asked to testify at last year’s confirmation hearings.
Mr Stier notified senators and the FBI during the confirmation process that he saw Mr Kavanaugh with his pants down before friends pushed the freshman’s penis into the woman’s hand.
However the FBI did not investigate his account, the Times reported. Both Mr Stier and Mr Kavanaugh refused to discuss the allegation with the newspaper.