The Parisian costume party featured a man in a dog collar, a dwarf, a nearly naked nun _ and a rather well known guest named Pippa Middleton, younger sister of the Duchess of Cambridge.
Middleton, 28, was in the headlines Tuesday, with photographs of her appearance at a friend's decadent birthday party splashed across the Daily Mail tabloid.
The pictures are striking: women in revealing, low-cut period costumes from the 18th-century playacting with men in fancy clothes and spiky leather collars and bracelets.
Buckingham Palace declined to comment, but the racy coverage was likely not well received by Britain's royal family, which has been enjoying a popularity boost since the former Kate Middleton's fairytale wedding to Prince William last year.
"A lot of the world considers that she (Pippa) is royal, and by association what she does has an influence on the royal family," said Ingrid Seward, editor of Majesty magazine.
"It's unfortunate for Pippa, it's quite difficult for her," Seward said of the tabloid reports. "She has all the downside and not the upside. I know she had has a very hard time."
Pippa Middleton holds no royal title, but her life has been subject to intense scrutiny since she captured attention at her sister's wedding with a close-fitting maid of honor dress.
The picture editor at the Daily Mail, Paul Silva, recently said that up to 400 paparazzi shots of her cross his desk every day.
Britain's media often characterize her as the party-loving, more vivacious contrast to the elegant and subdued Duchess.
The Daily Mail story _ with the headline "Her Royal Hotness and the viscount in a dog collar" _ showed Middleton, dressed in an 18th-century style top, posing with other similarly dressed women and a man in a king's costume laughing as one of the women pulled on the dog collar around his neck.
The article said the man was the host, Arthur de Soultrait, a French fashion designer.
The paper ran other photos from the party that featured a woman in scanty lingerie and a nun's headdress dancing with a dwarf.
The story came after photographs in The Sun newspaper Monday that showed Pippa Middleton in a convertible, next to a companion who pointed what appeared to be a gun at the photographer.
A spokesman for a French clothing company owned by de Soultrait, who also appeared to be in the car, denied that Middleton's companion brandished a pistol at the paparazzi, saying that the driver was in fact "playing a game" with the photographers with a toy gun.
Paris police say they've received no complaint and are not investigating the incident.
Regardless, it seemed that the harm has been done.
"It's very damaging for her, it's a totally irresponsible, stupid thing to do," said Max Clifford, one of Britain's best-known public relations gurus.
Clifford said that although Pippa wasn't a member of the royal family, she needed to be much more careful about her behavior.
"(Princes) William and Harry have been such a PR success for the palace. The last thing the royals need is someone like this," he added.