Twenty-three Chinese swimmers tested positive for the banned drug TMZ months before the Tokyo Olympics in 2021, it has emerged. However, they were cleared to compete at the Games after the World Anti-Doping Agency (Wada) accepted an explanation from the Chinese authorities that the kitchen at their hotel was contaminated.

The story, which has come to light after a joint investigation by the German TV channel ARD and the New York Times, has led to widespread criticism of Wada from senior figures in anti-doping, with one calling the case “shocking” and another a “devastating stab in the back to clean athletes”.