Keri Claussen Khalighi, now 43, has accused recording mogul Russell Simmons of forcing himself on her when she was a 17-year-old model.
Khalighi alleges that she met Simmons and Ratner at a casting call before accompanying them to dinner in New York in 1991.
The trio then went back to Simmons' apartment to watch a music video the two men had been working on.
Khalighi alleges that Simmons began to make 'aggressive sexual advances' towards her and took off her clothes – she alleges that Simmons later penetrated her without permission in the shower.
She revealed: "I looked over at Brett and said 'help me' and I'll never forget the look on his face.
"In that moment, the realization fell on me that they were in it together."
The model alleges that Simmons tried to force her to have sex but that she 'fought it wildly' before she eventually 'acquiesced' and performed oral sex.
She states that Ratner – who was a video director at the time – 'just sat there and watched'. Khalighi ten went for a shower but Simmons reportedly followed her before briefly penetrating her in the shower without her consent.
"'It hurt so much," she said.
Both Simmons, 60, and Ratner, 48, have denied the allegations.
In a statement Simmons strongly disputed her account.
He said: "Everything that occurred between Keri and me occurred with her full consent and participation, "Much of the two days and one night he spent with her, he said, was with other people, or in public."
While Ratner had 'no recollection' of Khalighi asking him for help and denied witnessing her 'protest' said his attorney Marty Singer.
Film producer Ratner – who has been met with several allegations of sexual misconduct by various women – filed a defamation lawsuit against Melanie Kohler in a Hawaii federal court after she made similar allegations against him.
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