Duane Martin Won't Respond to Allegation He Had Sex with Will Smith

Duane Martin's going to let Will Smith and Jada Pinkett Smith deny the allegation he had sex with Will, but Duane's not jumping into the fray himself.

Sources familiar with the situation tell TMZ ... Duane has no plans to publicly respond to the claim, because the allegations are so ridiculous.

As we reported, Brother Bilaal -- who claims to be a former friend/assistant to the actor -- alleges he once walked in on Will and Duane having anal sex in a dressing room.

Bilaal told Tasha K, "I opened the door to Duane’s dressing room and that’s when I see Duane having anal sex with Will. There was a couch and Will was bent over the couch and Duane was standing up killing him, murdering him. It was murder in there."

Will's team is denying the allegation, telling us ... "This story is completely fabricated and the claim is unequivocally false." They also said Will is weighing his legal options.

Meanwhile, Will's wife was more definitive ... we got Jada Wednesday morning in NYC, and she told us the Smiths are, indeed, planning to respond with a lawsuit.

Bottom line for Duane, though ... he won't dignify the whole mess with a response.