Levy won the prize for her novel Small Island

Levy, from north London, won the �30,000 award, which recognises women writers, for her novel Small Island.

"I was shocked - I didn't think this would happen," she told BBC News Online. "It was a fantastic shortlist with fantastic authors."

Other nominees included Gillian Slovo, Margaret Atwood, Rose Tremain and Shirley Hazzard.

Small Island, Levy's fourth novel, focuses on a Jamaican couple who arrive in Britain to begin a new life after World War II.

ASK THE AUTHOR You put your questions to Andrea Levy in an interactive forum. Click here to watch the forum. (opens a new window)

The book is based on the experiences of Levy's own parents, who were among the migrants who came to Britain on the Windrush in 1948.

"It's very much part of my personal history," Levy said, "so I very much wanted to go back and have a look at what immigration means, not only for the people that come but for the people who are here."

Levy admitted she had been "overwhelmed" to be on the shortlist.

"When I was told I was on the shortlist I was obviously really pleased," she said, "and now with this, I'm absolutely convinced I'm dreaming."

Shortlist

She added that there was a real need for the prize, which was first awarded in 1996 and has in the past been won by such authors as Helen Dunmore and Carol Shields.

"It's doing its job," Levy said, "It's really bringing women's fiction out to a wider public, and without it we'd feel the loss."

ORANGE SHORTLIST Margaret Atwood - Oryx and Crake Shirley Hazzard - The Great Fire Andrea Levy - Small Island Chimamanda Ngozi Adichie - Purple Hibiscus Gillian Slovo - Ice Road Rose Tremain - The Colour

The 20-strong shortlist was whittled down to the final six by a panel of judges, including comedian and broadcaster Sandi Toksvig and author Minette Walters.

"It was a tremendously strong shortlist this year. What was particularly interesting was that many of the books were historical this year," Orange Prize founder Kate Mosse told BBC Radio 4's Today programme.

"I think that's something to do with idea that we have finished a big century and now we are starting a new century and there is the opportunity to look back and see things, not as they happened contemporaneously, but in the context of the broader picture."

Suzie Doore, fiction buyer for Waterstone's, praised the judges' decision.

"Andrea Levy is a wonderful writer who really deserves a huge readership," she said.

"This prize is fantastic news for her as it will bring her work to the attention of a lot more readers."

Increase

Last year's winner was US author Valerie Martin, who won for her Gothic American thriller Property, set in slavery days Louisiana.

After her win the sales of her book climbed to more than 1,500 copies a month for six months - with 2,500 a month before Christmas.

Margaret Atwood was on the shortlist

The 2002 winner, Bel Canto by Anne Patchett, saw an even bigger increase, with sales of around 3,000 a month after her win and a peak of 6,000 a month during the pre-Christmas period.

The sales figures, however, cannot compete with the Booker prize, which was last year won by DBC Pierre's Vernon God Little.

The book saw its sales increase to more than 12,000 copies a month after its author won.

The previous year's winner, Yann Martel, saw sales of his novel The Life of Pi soar to over 30,000 a month.