An actress has accused Jeremy Piven of sexually harassing her on the set of Entourage.
Ariane Bellamar, an actress and reality star, made the allegations on Twitter, saying the Emmy-winning actor repeatedly groped her on set.
"Jeremy Piven, on two occasions, cornered me and forcefully fondled my breasts and bum. Once at the [Playboy] mansion and once on set," Bellamar wrote, using the hashtag #MeToo.
She also accused the actor of sending her "sexual and threatening texts".
In a statement to Deadline, Piven said the incidents "did not happen".
"I unequivocally deny the appalling allegations being peddled about me," he said.
"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."
Piven, 52, won three Emmys and a Golden Globe for his portrayal of manic Hollywood agent Ari Gold in the HBO series and its subsequent film.
He currently stars in the new CBS drama Wisdom of the Crowd, which premieres on Ten on Sunday.
"We are aware of the media reports and are looking into the matter," a spokesperson for CBS told Hollywood Reporter about the allegations.
Entourage, which ran on HBO from 2004 to 2011 and followed the sexual exploits of fictional Hollywood star Vinnie Chase (Adrian Grenier), has long drawn criticism for its depiction of male entitlement, extending to its behind-the-scenes culture.
In June, actress Alison Brie described a casting audition for the show early in her career, during which producers asked her to take off her top.
In a statement on Wednesday, the cable network said today's press reports were the first they'd heard of Bellamar's accusations.
"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," the network said.
Piven has faced previous criticisms over his on-set behaviour.
In 2015, Will & Grace star Debra Messing said she "wasn't a fan" of the actor, after he guest-starred on the comedy hit's third season.
"The very first day of rehearsal, he shoved his tongue all the way down to my heart... I was just like, 'Woah!'" she told chat show host Andy Cohen.
The accusations against Piven follow renewed focus on sexual harassment in Hollywood, in the wake of claims against producer Harvey Weinstein, director James Toback and, most recently, House of Cards star Kevin Spacey.
On Tuesday, veteran sitcom star Andy Dick was fired from the upcoming indie film Raising Buchanan over multiple sexual misconduct claims on set, including groping, non-consensual licking, and propositioning castmates and crew.
"My middle name is 'misconduct', they know what they signed up for," the controversial actor, 51, told Hollywood Reporter.
While he denied "groping anyone", he admitted to propositioning others on set.
"I don't know the difference between sexual harassment and trying to get a date," he said. "In the '70s, all the girlfriends I got was by kissing and licking their cheek. I don't know anymore."
???Member when I tried to leave; you grabbed me by the ass, looked at yourself in the mirror, & said what a ???beautiful couple' we made? #MeToohttps://t.co/liD7irs0o0??? Ariane Bellamar (@ArianeBellamar) October 30, 2017
I was led to @jeremypiven's trailer by a young, blonde woman w/a clipboard (I presumed a PA) to discuss my ???career'. My ???potential'. #MeToopic.twitter.com/rpQwJHVXRu??? Ariane Bellamar (@ArianeBellamar) October 31, 2017