Nicole Kidman refused to use the "N' word" in her controversial movie The Paperboy.

The Oscar-winner stars alongside Zac Efron in the dark thriller, which involves various explicit sex scenes.

Despite pushing the boundaries for her role, Nicole knew where she had to draw the line.

"I asked her to use the 'N' word," director Lee Daniels revealed during a press conference.

"I could feel the racial tension there in the town. She said, 'I won't do it.' I told my producer, 'She won't do it!' Then he mapped it out Lee, day one she is on a washing machine, day two she is urinating on Zac Efron, day three she's having telepathic sex I think you can forgive her."

Nicole has two adopted children, Isabella and Connor, with her ex-husband Tom Cruise, and also raises daughters Sunday Rose and Faith Margaret with current spouse Keith Urban.

Personal reasons helped her decide not to use the term.

"I just didn't feel it was right for the character," Nicole explained.

"I have a son [Connor] who is African American. I just didn't feel like it was right. What I try to do as an actor is fulfilling a director's vision. I have opinions, but at the same time I'm not there to stop him from anything. I've really tried to do that in every film. I never want to pull them off their vision."