Andrew Mountbatten-Windsor and Jeffrey Epstein asked an exotic dancer to "engage in various sex acts" at the late convicted sex offender's Florida home, a legal letter claims.
In a letter released as part of the latest tranche of Epstein files, the unnamed woman's lawyers said she had been offered $10,000 to dance and that after she performed Epstein and Mountbatten-Windsor had asked for a threesome.
Lawyers said the woman had not been paid the promised amount and would keep the alleged 2006 encounter in which she was "treated like a prostitute" confidential in exchange for a payment of $250,000.
BBC News has contacted Mountbatten-Windsor for comment. He has always denied any wrongdoing.
The letter, dated March 2011, claims that the woman and other exotic dancers from "Rachel's Strip Club" in West Palm Beach had been chauffeured to Epstein's house and offered $10,000 to perform.
The document claims that she had seen "other young women dressed provocatively" at the party, some of whom "appeared to be as young as 14 years old".
After she arrived, she was directed upstairs where she was introduced by Epstein to Mountbatten-Windsor, the letter says.
It alleges: "My client then danced for the men, undressing until she was wearing only a bra and panties. Mr. Epstein and Prince Andrew then told my client they wanted to have a threesome.
"She said she was hired to dance, not to have sex. Mr Epstein said they would pay her later for dancing, and they prevailed upon her to engage in various sex acts."
The letter claims that "after the men had satisfied themselves" she was invited to take a trip with the pair to the Virgin Islands, which she declined.
Lawyers said she had only been paid $2,000 of the promised fee of $10,000.
The woman had not previously pursued the claims because she was "not proud of the circumstances of that night," the letter says. "She was working as an exotic dancer, but she was treated like a prostitute."
Mountbatten-Windsor is under mounting pressure to give evidence about his relationship with the late convicted sex offender.
Photographs appearing to show the former prince kneeling on all fours over a female lying on the ground were included in the latest batch of Epstein files released by the US Department of Justice on Friday. Both are fully clothed.
