Swetnick said in a statement released by her lawyer that events took place at parties she attended while high school student in Maryland.
Washington: A new woman claimed on Wednesday to have witnessed sexually abusive behaviour by Brett Kavanaugh and said she was gang-raped at a party in the early 1980s attended by the Supreme Court nominee.
Julie Swetnick said in a statement released by her lawyer that the events took place at parties she attended while a high school student in suburban Maryland.
She said she saw Kavanaugh behave as a "mean drunk" at such parties and witnessed him "engage in highly inappropriate conduct" that included the "fondling and grabbing of girls without their consent."
"I observed Brett Kavanaugh drink excessively at many of these parties and engage in abusive and physically aggressive behaviour towards girls, including pressing girls against him without their consent, 'grinding' against girls, and attempting to remove or shift girls' clothing to expose private body parts," Swetnick said.
"I likewise observed him be verbally abusive towards girls by making crude sexual comments to them that were designed to demean, humiliate and embarrass them," she said.
Swetnick said Kavanaugh's claim of "innocence" and lack of sexual activity in high school was "absolutely false and a lie."
Swetnick, who has worked extensively for the US federal government, also said she was drugged and gang-raped at a party in approximately 1982 at which Kavanaugh was present.
She did not claim that Kavanaugh took part or was aware of her rape but she claimed that he and other boys in his circle engaged in similar behaviour.
She said she had witnessed efforts by Kavanaugh to "'target' particular girls so they could be taken advantage of."
The bombshell new claims come after two women came forward to accuse the judge of assaulting them in the 1980s, in a scandal that has tripped up what was expected to be an easy confirmation process for the conservative judge.
At a crunch Senate hearing on Thursday, California university professor Christine Blasey Ford will detail allegations that Kavanaugh assaulted her at a high school party when they were both teenagers.
Kavanaugh also stands accused of exposing himself to a classmate, Deborah Ramirez, causing her to touch him without consent, during an alcohol-fuelled Yale University party a few years later.
Kavanaugh was handpicked by Donald Trump for the lifelong post on the Supreme Court, and has continued to enjoy the US president's steadfast support despite the allegations against him.
Swetnick's statement was released by her lawyer, Michael Avenatti, the attorney for porn star Stormy Daniels, who has claimed to have had a sexual encounter with Donald Trump.