A statement released by the World Anti-Doping Agency (WADA) has questioned the integrity of the U.S. Anti-Doping Agency (USADA), which has allowed athletes who had doped to compete for years, in direct contravention of the World Anti-Doping Code and USADA's own rules.

"This USADA scheme threatened the integrity of sporting competitions, which the Code seeks to protect," read the statement. "Contrary to the claims made by USADA, WADA did not sign off on this practice of permitting drug cheats to compete for years on the promise that they would try to obtain incriminating evidence against others."

WADA also said it found at least three cases where athletes who had committed serious anti-doping rule violations were allowed to continue to compete for years while they acted as undercover agents for USADA, without notifying WADA.

It then elaborated with several detailed examples. "In one case, an elite-level athlete, who competed at Olympic qualifiers and international events in the United States, admitted to taking steroids and EPO, yet was permitted to continue competing all the way up to retirement."

"Their case was never published, results never disqualified, prize money never returned, and no suspension ever served."

WADA did not name the athletes in question, citing security concerns in case they faced retaliation.

WADA also called it "ironic and hypocritical" that USADA suspected other doping organizations, while USADA allowed cheats to carry on competing on the off chance they might help them catch other possible violators.

(Cover: The World Anti-Doping Agency office. /CFP)