Actress Kristina Cohen has accused Gossip Girl star Ed Westwick of raping her three years ago.
The actress, 27, detailed the allegations in a Facebook post, saying the alleged assault occurred at the actor's Hollywood Hills home the first time she met him in February 2014.
Westwick, 30, the British actor who rose to fame playing Chuck Bass on the teen drama, has bluntly denied the accusations.
In her Facebook post, Cohen said she was dating a producer - who she later identified as Australian Kaine Harling - who was friends with Westwick at the time of the alleged incident.
"It was this producer who brought me up to Ed's house where I met Ed for the first time," she wrote.
"I wanted to leave when Ed suggested 'we should all f---'. But the producer didn't want to make Ed feel awkward by leaving."
Cohen said that after stating she was tired and wanted to leave, Westwick suggested she nap in his guest bedroom while the two men smoothed over the "uncomfortable situation".
"I went and laid down in the guest room where I eventually fell asleep. I was woken up abruptly by Ed on top of me, his fingers entering my body," Cohen wrote.
"I told him to stop but he was strong. I fought him off as hard as I could but he grabbed my face in his hands, shaking me, telling me he wanted to f--- me.
"I was paralysed, terrified. I couldn't speak, I could no longer move," she continued. "He held me down and raped me."
Cohen's friend, actor Blaise Godbe Lipman, and sister Katalina Colgate, both told Deadline that Cohen had told them of the alleged assault at the time, "a few days after Valentine's Day" in 2014.
On Wednesday, Westwick took to Instagram to hit back at the accusations.
"I do not know this woman. I have never forced myself in any manner, on any woman. I certainly have never committed rape," he wrote.
In her post, Cohen said she was "sickened" to see Westwick later honoured by Oxford University's student union as one of their 'People Who Shape Our World'.
"How does this end? Men like Ed using their fame and power to rape and intimidate but then continue through the world collecting accolades," Cohen wrote.
The LAPD was investigating the claims as of Wednesday morning, Deadline reported.
Westwick is the latest Hollywood star to face accusations of sexual assault or harassment, after an expose on movie mogul Harvey Weinstein shone a spotlight on the industry's culture of sexual misconduct and abuse.