Michelle Williams refused to accept the role of Marilyn Monroe in a new movie without auditioning - because she was determined to prove she's capable of playing the blonde bombshell.

Moviemaker Simon Curtis asked the Brokeback Mountain star to play the screen icon in upcoming biopic My Week With Marilyn, but Williams was wary of taking on the role.

Curtis eventually convinced her to tackle the part - but Williams insisted on playing a scene in character to show him she was truly talented enough.

She tells Britain's Elle magazine, "I said, 'I want both of us to know that I can do this, I don't want to be offered this role for any other reason than we know that I'm capable of it.'"

The actress also admits her early days shooting the movie were daunting, adding, "I was so scared. I think after the second day, I told them they had to take away my passport because I was a flight risk - I wanted to hop on the next train to the Alps or something and get the hell out because it was terrifying."