Private eye Richard Di Sabatino — who has protected Robert De Niro, Nicole Kidman and other high-profile clients — claims “Ray Donovan” creator Ann Biderman took the idea of the hit Showtime series from him six years ago. Di Sabatino was working with director Michael Mann at the time on a movie for Universal. “They brought Biderman in as the writer,” Di Sabatino told The Post’s Richard Johnson. The hero of the story was “a fixer” in the LA area who works through a law firm and clashes with his father, who was a former cop in Di Sabatino’s story. “She changed the father from a cop to a hoodlum,” the private eye said. Jon Voight plays the gangster father of the fixer Ray, played by Liev Schreiber. “He’s a guy who fixes everyone else’s problems, but can’t fix his own,” Di Sabatino said. Biderman, who produced the NBC cop show “Southland,” claimed she needed more time to develop the story, and the project stalled. Biderman stopped returning Di Sabatino’s calls. He also says she allegedly appropriated a scene from Anthony Pellicano, the LA private detective doing hard time for wiretapping. “Before sitting down with me, she had worked with Pellicano on a show for HBO,” Di Sabatino said. “In one scene, the fixer catches a stalker and, with a baseball bat in his hands, tells him, ‘the bat or the bag.’ ” The stalker picks the bag, which has packages of green dye, and he is forced to dye himself in the bathtub. “Biderman used the same scene in the opening episode of ‘Ray Donovan,’ ” Di Sabatino said. His lawyer, Tom Harvey, is mulling a suit against Biderman, and Di Sabatino is planning to write a book, “The Real Ray Donovan.” Showtime had no comment. But at a junket last winter, Biderman told reporters: “I know a number of private investigators and did a tremendous amount of research and did extensive interviews with people.”