Natalie Portman always thinks twice before agreeing to strip off on film - because she fears her naked image will end up on pornography websites.

The actress admits she struggled with the decision to appear nude at the start of her career, and even asked filmmakers to rewrite a scene in her 1999 movie Anywhere But Here because she felt uneasy about baring all.

She tells America's V magazine, "I was figuring out my own sexual identity, likes and dislikes and all that stuff, and it's weird to be doing stuff on film as you're figuring it out. Also being a sexual object when you're a kid is really uncomfortable. After The Professional, I was already getting creepy letters."

Portman insists she would sign up for more film roles that require her to shed her clothes - but she worries the footage will eventually hit the web.

She adds, "It's annoying because online bulls**t interferes with what I want to do artistically. I'm not opposed to sexuality or nudity in a film, but I'm very opposed to pornography sites and you're pretty much giving them material if you do any of that. It's always a big dilemma for me."