Jason Kempin/Getty; Fred Duval/FilmMagic; Todd Oren/WireImageBret Lockett (l.) claimed he had an affair with Kim Kardashian while she was with Kris Humphries.
The 24-year-old athlete claims in the magazine's new issue that Kardashian, 30, "pursued" him last year after being connected through actress Lauren London and Lockett's brother Colin.
"I was talking to Lauren about my brother, and she said Kim Kardashian wanted Bret's phone number," Colin alleged. "They chatted, and then they started texting each other."
Kardashian allegedly sent Lockett a photo of herself and discussed vacationing together, though they never went on to meet in person over the five-month correspondence.
"I knew this was a game to her," Lockett told In Touch, "and this is what she does."
But Kardashian, who became engaged to 26-year-old Humphries of the New Jersey Nets on May 18 after six months together, completely denies the allegations and even had her attorney warn the magazine not to publish the false story.
"The story is absolutely not true," a rep for Kardashian told the Daily News. "Kim does not even know who this guy is."
In a letter obtained by TMZ.com, lawyer Dennis A. Roach said publishing "the factually untrue and unsubstantiated information" would be "at a minimum, damaging, defamatory and an invasion of her privacy."
He also noted that London's attorney has confirmed that she played no role in the story, claiming a "third party is impersonating" her, and added that he would be "forced to take appropriate legal action" if the magazine went ahead with it anyway.
Shortly after the story went public, Kardashian took to her Celebuzz blog to further shoot down the cheating claim.
"This guy should be ashamed of himself. Calling up a magazine and making up an entirely fake story in a sad attempt to ruin my relationship!?!?! It's just shameful and this guy should feel ashamed and humiliated," she wrote.
"Is this your pathetic attempt for attention? I'll be damned if anyone, especially some loser I've never even met, is going to try to come between Kris and I."
Kardashian's rep confirmed to the Daily News she is now planning to sue.