Keira Knightley said she drank vodka and champagne to help her film several intense sex scenes in her latest movie A Dangerous Method.

The thriller sees Keira paired with Irish co-star Michael Fassbender in a series of explicit sex scenes, including one involving spanking.

"We were both very nervous about those scenes because they’re not nice," Keira told the Daily Mirror. "We had a couple of shots of vodka before doing the scene and a couple of glasses of champagne afterwards."

The 26-year-old actress plays psychoanalyst Sabina Spielrein, who falls for Michael in the role of Carl Jung.

"When we shot them (the sex scenes) I said to Michael, 'If you touch me I’m going to kill you,'" she said. "He said, 'Keira, you’re tied to the bed at the moment. I don’t think you’re in any position to say that."

The star admitted she was initially put off the film because of the extreme sex scenes.

"When I read it I loved the script and really wanted to play the character, but I didn’t want to do those scenes," she said.

"I phoned the director David Cronenberg and said I was going to have to turn it down. He said he really wanted me to play the part so he’d take the scenes out. But I said, 'Whoa!' because I knew they were incredibly important to the story.

"He said he didn’t want the scenes to be sexy or voyeuristic, he wanted them to be clinical and a complete exploration of what she was feeling. So we kind of came to an agreement with Michael as well – because he had questions about the scenes, too. I wanted it to be as shocking as possible without going over the top."

Because of the dark nature of the film, Keira and her co-stars did everything they could to alleviate the atmosphere inbetween shoots.

"When you’re playing something so dark you want to have a really nice time afterwards otherwise it’s far too depressing," she explained.

"The actual filming work was very focused and very creative, but at the end of the day we watched football – the World Cup was on – and drank beer."

Keira Knightley's sex scene aid