has denied the "appalling allegations" Ariane Bellamar has made against him. Bellamar says Piven sexually assaulted her.
The 52-year-old actor has been accused of groping the Playboy Playmate and reality star on the set of his TV show "Entourage" -- in which he played Ari Gold for eight seasons between 2004 and 2011 -- and again at the Playboy Mansion, but he insists the claims are false.
Bellamar tweeted on Monday, "Hey @Jeremy Piven! 'Member when you cornered me in your trailer on the Entourage set? 'Member grabbing my boobies on the [couch] without asking??"
"Member when I tried to leave; you grabbed me by the a**, looked at yourself in the mirror, & said what a 'beautiful couple' we made? #MeToo."
"Jeremy Piven, on two occasions, cornered me & forcefully fondled my breasts & bum. Once at the mansion & once on set."
Bellamar said she was led to his trailer to discuss her career before he groped her. She also said he sent her "abusive, explicit texts."
In response, Jeremy insisted the alleged incidents "did not happen" and hoped Bellamar's claims "do not detract" from other women who have come forward with claims of sexual misconduct against them in the wake of the Harvey Weinstein scandal.
He said in a statement: "I unequivocally deny the appalling allegations being peddled about me. It did not happen.
"It takes a great deal of courage for victims to come forward with their histories, and my hope is that the allegations about me that didn't happen, do not detract from stories that should be heard."
HBO, who broadcast "Entourage," insisted they had no idea about the claims.
They said in a statement: "Today, via the press reports, is the first we are hearing about Ariane Bellamar's allegations concerning Jeremy Piven.
"Everyone at HBO and our productions is aware that zero tolerance for sexual harassment is our policy. Anyone experiencing an unsafe working environment has several avenues for making complaints that we take very seriously."
CBS, which airs Jeremy's "Wisdom of the Crowd" said they are "looking into the matter."
However, Bellamar insists they haven't reached out to her or her team.
She wrote on Twitter, "So interesting that @CBS stated today that they are investigating the @jeremypiven issue, yet neither myself or my reps have been contacted."
"Not much of an investigation if you're only investigating one party, no?"