Adichie's novel was selected for the Richard and Judy Book Club

She beat five other contenders for the �30,000 women-only award, including Kiran Desai, shortlisted for her Booker Prize winner The Inheritance of Loss.

Adichie's novel, Half of a Yellow Sun, is her second work and set during the Biafran War of the 1960s.

The new writer's award worth �10,000 was presented to Karen Connelly for her novel The Lizard Cage.

Moral responsibility

Adichie's first novel, Purple Hibiscus, was also shortlisted for the award - formerly known as the Orange Prize for Fiction - in 2004.

Bookmakers Ladbrokes made her favourite to clinch the honour after a flood of bets in recent days.

Desai would have become the first author to win both the Orange and Booker Prizes for the same novel if she had triumphed.

CHIMAMANDA NGOZI ADICHIE FACTS Born 1977 in Aba, Nigeria Was educated in the university town of Nsukka Has a Masters degree in creative writing from Johns Hopkins University in the US Was a Hodder Fellow at Princeton University, teaching introductory fiction Divides her time between Nigeria and the US

Half of a Yellow Sun tells the story of people caught up in the unfolding political turmoil in west Africa, whose loyalties are acutely tested when troops advance on the dusty university town they inhabit.

The novel examines ethnic allegiances, moral responsibility, class and race.

The award ceremony took place at the newly-refurbished Royal Festival Hall on London's South Bank, and the judging panel included broadcaster Muriel Grey and best-selling writer Marian Keyes.