Filmmaker Roman Polanski
Filmmaker Roman Polanski has been accused by a third woman of rape as a minorREUTERS/Kacper Pempel/File Photo

Film director Roman Polanski has been accused by a third woman of sexual assault when she was a minor.

The woman who was only named as Robin said that when she was 16, she was "sexually victimised" by the director back in 1973 in southern California.

The statute of limitations has expired but she could be called to testify in any future trial of the director.

She said she was prompted to come forward after Samantha Geimer, who was 13 when she was raped by Polanski in 1977, had asked for the case to be put to rest.

Reading from a prepared statement, she said: "The day after it happened, I did tell one friend that Mr Polanski had done that to me.

"The reason, with this exception, that I kept it to myself is that I didn't want my father to do something that might cause him to go to prison for the rest of his life."

In the Geimer case, Polanski admitted statutory rape and apparently been promised that he would not serve any further time in prison, but fled to France when he thought the judge was going to scrap his plea deal and jail him. He is still wanted in the US.

In 2010, British actress Charlotte Lewis claimed the director "forced himself" upon her just after her 16th birthday.

Polanski's attorney could not immediately be reached for comment, AFP reported.

Born in Poland, Polanski directed the acclaimed films Rosemary's Baby and Chinatown. He turns 84 on Friday (18 August).