Ex-‘Baywatch’ hunk Michael Bergin is a despicable cad, reveals a woman who dated him — and she wouldn’t believe a single scandalous thing he says in his new book about JFK Jr.‘s late wife Carolyn Bessette!

“Michael Bergin’s a liar — and I should know, I slept with him!” actress Wendi Winburn tells The ENQUIRER in an exclusive interview.

Bergin, 35, claims in his controversial kiss-and tell that he and Carolyn had a torrid affair during her marriage to JFK Jr. that ended shortly before she and John were killed in a plane crash July 16, 1999.

Carolyn can’t defend herself against the embarrassing charges the former Calvin Klein underwear model makes in “The Other Man: A Love Story: John F. Kennedy Jr., Carolyn Bessette, & Me.”

But Wendi, 34, a pretty blonde who bears a striking resemblance to Carolyn, can.

“It’s ridiculous that he’s claiming Carolyn chased after him,” she said.

Bergin first broke Wendi’s heart at a celebrity bachelor auction for Big Brothers of Greater Los Angeles in 1999.

“I always thought he was a babe,” she said. “So I bid on a date with him for $2,000, and I won!

“But when I went to meet him after the auction and ‘pick up’ my prize, he wasn’t even there! It was just me and a stupid poster of the guy.

“I’d just put $2,000 towards charity for him and he didn’t even bother to show up. I didn’t even get a hug or a picture with him.”

Hurt and embarrassed, she waited a few weeks, but still didn’t hear from him.

“Finally, I called Big Brothers and they apologized, and told me they’d contact him. I felt like they were twisting his arm to do the charity he’d already promised,” she said. “When he phoned after three months, he told me he’d take me to the premiere of Adam Sandler‘s movie, ‘Big Daddy,’ I guess so he could be seen doing his supposed ‘charity’ work.

“When he picked me up, he kept telling me about how he was a huge commitment-phobe, so that I wouldn’t get any ideas of actually dating him.” At the premiere, Bergin was all hands, she said.

“He was kissing and groping me,” Wendi recalls. “He seemed eager to come back to my place if I’d wanted. But I didn’t … and he never called back. That’s pretty rude!”

A year later, she said she bumped into Bergin again at the Koi restaurant in West Hollywood.

“He was so sweet,” she said. “He never mentioned any girlfriend or anything. I was so gullible. I kept thinking: ‘Oh my God, I could be his girlfriend!’

“I was such an idiot.

“That night when he asked me if he could come over, I let him and we spent the night together.

“At 6 a.m. the next morning, he nervously said that he had to get going.

“He asked for my number but I didn’t hear from him again. I was so disappointed.”

But her biggest heartbreak came two days later when she saw him at a bar on Sunset Blvd. watching the Lakers game with his girlfriend … and child.

“He had told me that he had a child, but it wasn’t clear that he was still seeing the mother of that child,” she said.

“That day Michael pretended like I didn’t exist, as if nothing had ever happened between us.”

That was the last encounter she had with Bergin, who is now engaged to longtime girlfriend, makeup artist Joy Tilk, who recently gave birth to their second child.

Wendi, who has had roles on TV’s “Pacific Blue” and “Malibu, CA,” said she hasn’t read Bergin’s new book, but she wouldn’t believe him if he told her the sky was blue.

“He’s so smarmy,” she said.

“As buff as he is, he doesn’t have a moral fiber in his body.” — TIM PLANT