Keira Knightley's screenwriter mother Sharman Macdonald has hit out at media rumors suggesting her daughter is suffering from anorexia - comparing the press to "playground bullies".

Knightley has long been dogged by rumors that her waif-like figure is the result of an eating disorder, but she has always denied this - blaming her genes for her naturally svelte figure.

Last year, the 23-year-old successfully sued a British tabloid newspaper for publishing an article which accused her of being anorexic and setting a bad example to young girls.

And the star's mother Macdonald can't understand why the media is so obsessed with her daughter's weight.

She tells British newspaper The Sunday Times, "She's always been thin. She's her daddy's daughter, with his long body."

"It's a playground situation that we're looking at with the press - it's a form of bullying - but what can we do?"