In opening statements in Sean Comb’s sex trafficking trial in New York City. The feds are laying out their case against the Bad Boy Records founder … making some graphic allegations.

Prosecutors claim at one “freak off,” Diddy made an escort urinate in Cassie’s mouth. They say Diddy was directing every step of the sex parties, and he expected the women to appear like they were enjoying themselves.

The feds say this all started when Cassie was 19 years old with a hit single … and they claim Combs often got violent with her.

Prosecutors say Diddy flew into a rage when he found out she was seeing another man … brutally beating her, kicking her in the back and flinging her around like a rag doll … and blackmailing her by threatening to release a video of her having sex with male escorts.

The feds say Cassie will testify too … as will some of the escorts, including one who allegedly saw Diddy assault Cassie and drag her by her face during a “freak off.”

Diddy is charged with 5 federal counts — 2 charges of sex trafficking, 2 charges of transportation to engage in prostitution, and a single count of racketeering conspiracy. He’s pled not guilty and his defense says the “freak offs” were consensual.

THE CULTURE KEEPER-