Nina Agdal, Jack Brinkley-Cook allegedly flipped on club guest after raunchy PDA session

Nina Agdal, a supermodel ex of Leo DiCaprio’s, was seen straddling new boyfriend Jack Brinkley-Cook at Montauk hot spot Gurney’s on Saturday night, but when the couple’s canoodling was caught by a guest — the lovers allegedly flipped.

A source said Agdal and Brinkley-Cook — the son of Christie Brinkley — were first spotted making out by a fire pit at the resort’s clubby deck after dining at Scarpetta.

“They were then escorted to a VIP area and she jumped on top of him and started straddling him,” said our surprised source. “They were dry humping, making out, and he had his hand up her shirt. They were really going at it . . . She was bouncing up and down in his lap.”

When the gobsmacked guest started snapping pics of the alleged midnight mating ritual, Agdal, 26, approached the cameraman: “She said, ‘Let me see your phone! Give me your phone,’ ” said the shutterbug p.r. pro of the incident. “She was saying, ‘You’ve got to delete those!’ ”

The source added Brinkley-Cook “came over and said, ‘What the f - - k?! Let’s go, right now!’ ” He apparently added, “I’m gonna beat the s - - t out of you!” The source said that a group of Brinkley-Cook’s pals then began chiming in.

When the guest refused to delete the pics and headed to the lobby, he said Agdal “was in tears. She was saying, ‘We were supposed to be at a wedding tonight,’ ” (and the hosts would learn they were instead at Gurney’s). The fotog agreed to erase the shots . . . if Brinkley-Cook apologized. Instead, Brinkley-Cook allegedly exclaimed, “F - - k that!”

A source who was with Agdal insisted to us the scenario was “over-dramatized.” “They were having a good time when Nina saw people snapping pics . . . which is invasive.” She “kindly asked them to delete the photos, please, as she knew the situation would escalate . . . and Nina walked back to the table.”

A rep for Brinkley-Cook, 23, insisted the couple was just “dancing” when “a photographer began snapping photos . . . in an aggressive manner and put a camera right in her face.”

When the pair asked him to delete the pics, the rep claimed it was the photographer who became “hostile.” As far as apologizing: “Jack refused — he was protecting his girlfriend and did nothing wrong.” The rep also said anyone else who got involved in the dispute were not friends.

(Via Page Six)