An official from the World Anti-Doping Agency assisted in a controversial investigation by the US Anti-Doping Agency which involved recruiting athletes to provide information on potential dopers, the Guardian understands.
An Observer investigation, which revealed last month how a Kenyan runner became an undercover agent, has sparked a war of words between the agencies, the two most powerful anti-doping organisations in world sport. Wada has accused Usada of breaching its code by recruiting athletes who had failed drugs tests to provide intelligence.
