Her rant came in the same week as pop star Pink released her single "Stupid Girls," attacking celebrities such as Paris Hilton, who Rowling scorns as a "talking toothpick."

The writer, who has sold more than 300 million copies of her books worldwide, also admits she fears for her two daughters, Jessica, 12, and 15-month-old Mackenzie, growing up in a "skinny obsessed world."

Her attacks came after the multi-millionaire read an interview with a young model.

She wrote on her website: "She can talk about eating absolutely loads, being terribly busy and having the world's fastest metabolism until her tongue drops off (Hooray! Another couple of ounces gone!)."

"But her concave stomach, protruding ribs and stick-like arms tell a different story. This girl needs help but the world being what it is they're sticking her on magazine covers."

Speaking about her daughters, she added: "I'd rather they were independent, interesting, idealistic, kind, opinionated, original, funny - a thousand things before thin."