Donald Trump had an affair with former Playmate of the Year Karen McDougal — whom he met at a party for “The Apprentice” in 2006 while married to his current wife, Melania, according to an explosive report Friday that details the great lengths to which the future president went to conceal his alleged indiscretions from the press.

McDougal wrote in an eight-page, handwritten note — which her friend John Crawford shared with the New Yorker’s Ronan Farrow — that Trump “immediately took a liking to me, kept talking to me — telling me how beautiful I was etc.

“It was so obvious that a Playmate Promotions exec said, ‘Wow, he was all over you — I think you could be his next wife,’” according to the piece, titled “Donald Trump, a Playboy Model, and a System for Concealing Infidelity.”

She said she was initially wowed by Trump.

“I was so nervous! I was into his intelligence + charm. Such a polite man,” she wrote. “We talked for a couple hours — then, it was ‘ON’! We got naked + had sex.”

But McDougal added that she was stunned when Trump offered her money as she was getting dressed after their romp.

“I looked at him (+ felt sad) + said, ‘No thanks — I’m not ‘that girl.’ I slept w/you because I like you — NOT for money’ — He told me ‘you are special,’” she wrote, according to Farrow’s account.

McDougal wrote that after their first tryst, she “went to see him every time he was in LA (which was a lot).”

Trump eventually introduced her to members of his family and took her to his private homes, including at Trump Tower, where he pointed out Melania’s separate bedroom, McDougal claimed.

He “said she liked her space,” McDougal said, “to read or be alone.”

During a 2007 party for Trump Vodka in Los Angeles, she said, she was seated at a table with The Donald, Donald Trump Jr., his pregnant wife, Vanessa, and Kim Kardashian.

And at an “Apprentice” bash at the Playboy Mansion, McDougal said, Trump told her he had asked his son Eric “who he thought was the most beautiful girl here + Eric pointed me. Mr. T said ‘He has great taste’ + we laughed!”

McDougal ended their nine-month affair in April 2007, according to the article.

She felt guilty and uncomfortable with some of the would-be president’s comments, like the time her friend brought up her relationship with an African-American man, and Trump said she liked “the big black d–k,” according to the report.

After their relationship ended, McDougal signed a limited life-story rights agreement granting the publisher of the National Enquirer, American Media Inc., exclusive ownership of her story in exchange for $150,000.

But the story never ran. Farrow suggested the Enquirer just wanted to bury it — a practice known as “catch and kill” — because AMI CEO David Pecker is pals with Trump.

McDougal said she didn’t understand the full extent of the agreement she’d signed and regretted her decision to sell the rights to her story.

The White House said in a statement that Trump denies having had an affair with McDougal.

“This is an old story that is just more fake news. The president says he never had a relationship with McDougal,” a spokesman told the New Yorker.

The story comes as porn star Stormy Daniels is planning a tell-all about her own tryst with Trump.