Want to win £10,000? Then prove that homeopathy works in proper clinical trials in which half the patients receive the treatment, half receive a placebo, and no one knows till the end who got what.

The challenge was issued on Monday by Edzard Ernst, professor of complementary medicine at the University of Exeter, UK, and science author Simon Singh, in the wake of what they call a smear campaign against them in response to their book Trick or Treatment, which explores the scientific evidence behind complementary remedies. “We’re saying to homeopaths, ‘put up or shut up’,” says Singh.

The …