She said: "I was terrified. At the moment I lived in a state of inner terror."

Natalie Portman - who previously shot a nude scene for short film 'Hotel Chevalier' - is also worried the lesb!an $ex sequence is overshadowing the plot of the film and worries it will make her be taken less seriously as an actress.

She added: "Nudity is something absolutely natural and I'm not prudish - but in a film it can be distracting. Doing 'Black Swan' I couldn't say no. The project is a huge opportunity for me to show a new me. I can't always play the nice mothers. My other problem is that single pictures are being taken out of context and put on the internet."

The actress - who studied psychology at Harvard College while shooting the 'Star Wars' prequels - also laughed off suggestions she is one of Hollywood's most intelligent actresses.

The 28-year-old star said: "I can guarantee you I'm not one of the most intelligent actresses of the world."

'Black Swan' is set in the highly competitive world of New York ballet and follows Natalie Portman's veteran ballerina character who finds herself locked in direct competition with a mysterious rival dancer.

Natalie Portman was "terrified" when she had to kiss Mila Kunis in her new movie 'Black Swan'.