"It is emphatically denied that the Duke of York had any form of sexual contact or relationship with Virginia Roberts. Any claim to the contrary is false and without foundation," Buckingham Palace said in a new statement.
Dershowitz went further, telling CNN the accuser should go to jail and the lawyers representing her should be disbarred. He's never even met Roberts, he said.
"I am telling the truth and I can prove it. They are lying, and I can prove it," he told CNN's "New Day."
"This is a zero sum game. Either I'll end up being disabarred and criminally charged or they will be. There's no gray area here."
Dershowitz said he was filing a sworn affidavit Monday denying the accusations, and was filing a motion "to intervene in the case." His legal team is "preparing disbarment and disciplinary papers," he said.
He challenged Roberts to charge him with rape, the "most serious crime anyone can imagine. If she does, she will go to jail for filing a false rape charge." Dershowitz offered to waive the statute of limitations and "any immunity."
Dershowitz threatens $100 million defamation suit
He also challenged Roberts' attorneys to make their accusation in public, rather than through a "privileged legal document."
"They will not state on your show, 'Alan Dershowitz had sex with this woman,' " Dershowitz said. "Because if they do that, they're in court the very next day being sued for defamation for $100 million."
The attorneys have previously refused to do so.
"We intend only to litigate the relevant issues in Court and not to play into any sideshow attempted by anyone," Roberts' attorney Brad Edwards said in an email to CNN on Friday after Dershowitz was quoted elsewhere in the media making similar remarks.
"We do not plead anything before carefully investigating all of the allegations first," Edwards wrote.
His co-counsel in the case, former federal judge Paul Cassell, was copied on the email.
The message included a statement from Roberts, whom the attorneys referred to as "Doe 3."
"I am looking forward to vindicating my rights as an innocent victim and pursuing all available recourse. It appears that I am now being unjustly victimized again. These types of aggressive attacks on me are exactly the reason why sexual abuse victims typically remain silent and the reason why I did for a long time. That trend should change. I'm not going to be bullied back into silence."
"It's the exact opposite" of trying to silence someone, Dershowitz said in the CNN interview. "Repeat the statements, so then I can sue you."
Roberts' attorneys did not immediately respond to a request for comment Monday.
The fallout follows a federal court filing
alleging that "Doe 3" was forced to have sex with several men when she was a teenager. Virginia Roberts made the allegations in a civil motion filed last week in U.S. District Court in southern Florida, joined by another unnamed woman.
While Roberts was not identified by name in the filing, her name was widely reported in the British news media over the weekend, and Buckingham Palace included it in the statement. (Dershowitz noted that in his CNN interview, it was CNN that identified her by name.)
Case involves billionaire's plea deal
The case centers on an American billionaire.
Roberts and another woman are seeking to join two other women who are arguing in federal court for the U.S. government to take a fresh look at its case involving Jeffrey Epstein, who pleaded guilty some years ago in Florida to a state charge of prostitution solicitation.
The investment banker agreed to a state plea deal in 2007 and began serving an 18-month sentence in 2008, according to The New York Times.
Epstein was the subject of a federal investigation, but a deal allowed him to plead guilty to the lesser state charge and avoid a potential federal case, the Times and the Washington Post reported.
Prince Andrew has been photographed with Epstein. The prince previously issued an apology for his friendship with the scandal-plagued billionaire.
Buckingham Palace took issue Monday with reports in which Roberts' father alleged that his daughter had met Queen Elizabeth II, Prince Andrew's mother. The Palace said there is no record of a meeting.
Andrew, who was on vacation when the media storm over the accusations erupted, returned to Britain late Sunday, the Palace said.
The court filing last week claims that Roberts "was forced to have sexual relations" with the prince in London, New York and on Epstein's private island in the U.S. Virgin Islands.
Dershowitz was also accused in the latest court filing.
"Epstein required Jane Doe #3 to have sexual relations with Dershowitz on numerous occasions while she was a minor, not only in Florida but also on private planes, in New York, New Mexico, and the U.S. Virgin Islands," the filing states.
"She said I had sex with her on Epstein's island. I was on his island once," Dershowitz said, adding that he was "never out of my wife and daughter's sight for the 24 hours I was on the island. She said I had sex with (her) on Jeffrey Epstein's ranch in New Mexico. I was there for about an hour once before the building was complete. Nobody was in the building, I just toured the building. She said I had sex with her on Jeffrey Epstein's airplanes. The flight manifests will prove conclusively I was never on any airplanes with her. She's making it up out of whole cloth."
Including the accusations in a "privileged legal document," he said, is "the legal equivalent of writing graffiti on a bathroom wall and then running away."