"These allegations are nonsense," the singer, 34, says in a statement to Entertainment Tonight.
A pal tells the new issue of Us Weekly (on newsstands now): "Fergie says nothing is wrong. Every time I ask her how married life is, she says, 'Awesome!'"
Adds another, "Josh told her it didn't happen, and she believes him."
Still, an attorney for the exotic dancer tells Us Weekly that his client, Nicole Forrester -- a 34-year-old mother of two -- has passed a lie-detector test and is in possession of racy texts from the Transformers star, 37, that corroborate the affair.
Forrester previously said on The Bert Show on Atlanta's Q100-FM that she and Duhamel "had lots of sex" at the $830-a-night St. Regis hotel after he came into the Tattletale club where she works in Atlanta. (Duhamel is in the city shooting the comedy, Life As We Know It.)
Forrester claimed that they watched a porno movie and hooked up. Forrester's lawyer, Romin Alavi, tells the new Us Weekly, "They fell asleep together, and he kept waking her up to have more sex."
Alavi also tells Us Weekly that Forrester didn't seek out the the National Enquirer (which offered her $20,000 for the story) in hopes of a payday.
"Josh bragged about what happened on the set of his movie, and someone called the Enquirer with the tip,” Alavi tells Us Weekly. "The Enquirer then came to Nicole."
For more on Duhamel's alleged fling - including how her wild partying has "pissed" him off, how long-distance work has caused "strain" in their 10-month marriage and whether friends think they'll weather this latest stripper scandal - pick up the new issue of Us Weekly today!