Previous winners of the Orange Prize include Lionel Shriver for We Need to Talk About Kevin (2005), Andrea Levy for Small Island (2004), and Valerie Martin for Property (2003).

Orange judges hailed On Beauty, the tale of a white English liberal professor at an US East Coast university, as a "literary tour de force".

The comic novel, which takes EM Forster's Howards End as a template, follows the professional rivalry between the professor and a successful black conservative academic.

Smith herself spent a fellowship year at Harvard University in 2002-2003.

The judging panel was chaired by BBC broadcaster Martha Kearney, with comedian and novelist Jenny Eclair, director of the Institute of Ideas Claire Fox, novelist and columnist India Knight, and children's writer Jacqueline Wilson.

Ms Kearney said the quality of writing had made choosing a winner unusually difficult.

But she said of Smith's novel: "This is a book which combines extraordinary characterisation with skilful and seemingly effortless plotting.

"It ranges from exposing the intimacies of family life to broader themes of aesthetics, ethics and the vagaries of academe."

Meanwhile, the £10,000 Orange Award for New Writers went to Naomi Alderman for Disobedience, a tale set in north London's Orthodox Jewish community.

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