Sophie Dahl is an Orange Prize judge this year

Her first book, fairy-tale style novella The Man With The Dancing Eyes, was a success when it was released in February.

Dahl, 23, the granddaughter of classic children's writer Roald Dahl, has signed for a reported �100,000 with Bloomsbury, who also publish JK Rowling's Harry Potter books.

She has begun writing the as yet unnamed book and it is likely to be published next year.

"We are thrilled to be publishing Sophie's second book and her first one was a great success," a spokeswoman for Bloomsbury said.

"It made the bestseller lists in the UK and America the moment it came out."

'Passionate'

Dahl is one of the country's most successful models, but sees her future in writing and acting, her agent Ed Victor told London's Evening Standard on Friday.

"Sophie wants to be a professional novelist in the future, as well as pursuing acting work," he said. "She is passionate about writing."

He was selling the film rights to The Man With The Dancing Eyes and Dahl hoped to co-write the screenplay, he added.

Dahl has been chosen as one of the judges of this year's Orange Prize, a move originally denied by the prize organisers when the news leaked out months early.