A Swingers’ sex party in the penthouse of the Mondrian SoHo came to a premature end on Saturday night, following a clash between hotel security and organizers. Sources tell us guests at the “SiN White Party,” thrown by Behind Closed Doors and School of Sex, were just getting into the swing of things when hotel guards demanded to police the event. Once they got a look at the racy goings-on, the party was shut down, and all were ordered to leave — including one overly amorous couple carrying on in the balcony of the penthouse overlooking the New York skyline. An e-mail was later sent to disappointed guests saying, “As we have many celebrity guests and high-profile members at every event, it is crucial that we protect our members’ privacy and did not allow any venue’s security to intrude on our events. We had so many hot couples and singles come out — and we, like you, were extremely disappointed as to what happened.” One event organizer, who would be identified only as Rocco, told Page Six: “We host sex parties for a very upscale and young crowd. This event was a mixer. But the hotel security insisted on policing the event. We value the privacy of our guests and shut the event down immediately.” He confirmed one couple, clad in underwear, had carried on enjoying themselves on the terrace, but “they eventually agreed to leave after being repeatedly asked to do so.” One disappointed guest, who asked not to be identified, told us, “The party followed a photo shoot. My girlfriend and I . . . were there for the orientation for beginners that the organizers offer called Swing School. Overall, it was a hot crowd and a fun time, even despite the early close.” A hotel source said: “The event was booked as a photo shoot/documentary. There were issues with music and noise, so security came up to investigate, but were barred entry by the production’s own security. But hotel staff noticed the ‘guests’ were in various different stages of undress and positions, so they were removed from the hotel. The swingers then tried to carry on the party in two other rooms they had booked for hair and makeup, and were completely removed from the hotel.” A hotel rep confirmed the swingers were asked to leave.