Marc Malkin

Madonna and Gwyneth Paltrow engaging in some same-sex smooching? Kiss those loose-lipped allegations goodbye!

A source close to the two insists Madge and the Oscar-winning actress never shared the on-the-mouth kiss that Madonna's brother Christopher Ciccone reportedly alleges in his upcoming memoir, Life With My Sister Madonna.

Ciccone claims that his sister once planted a passionate lip-lock on Paltrow in the wee hours during a New Year's party thrown by Donatella Versace.

But an eyewitness at the soirée insists nothing of the sort ever happened. "I was at that party and did not see anything at all like what was described," the partygoer says.

So far, celebs who Ciccone apparently dishes about in the book are keeping silent.

Paltrow's rep declined to comment. Madonna's ex-boyfriend Warren Beatty isn't saying anything either regarding Ciccone's story that Beatty once cornered him and grilled him on what it's like to be gay.

However, Madonna's rep, Liz Rosenberg, cracked to the Associated Press, "There is no subject that doesn't fascinate Warren Beatty."

Now, the big question: Will the book fascinate people enough to actually buy it when it's released July 15?

Other anecdotes reportedly include Madonna once calling her ex-husband, Sean Penn, "a paranoid control freak" (crickets from Penn's rep, too), and Demi Moore dancing with Ciccone at a drag queen club.

If this is the juiciest of the book, Life With My Sister ain't exactly sounding like Madonna Dearest.

"It's all too silly and a bit sad," a source said. "Poor Christopher seeking attention."

A rep for the book declined to comment.

Rosenberg told the AP that Madonna has not read the book. "I would have to assume she has come to terms with the fact that they do not have a close and loving relationship," she said. "And with the book coming out, I assume that will remove the chances of that ever happening."

In happier times, Ciccone worked closely with his sister, directing her Girlie Show tour in 1993 and designing her Upper West Side apartment in New York City. He's currently putting together a pitch for an interior-design reality show.