World Anti-Doping Agency president John Fahey has urged drug cheats to withdraw from this summer's London Olympics.
Fahey, 67, does not believe that anyone who uses banned substances could ever consider themselves an honest winner.
He said: "I say this in the clearest way possible - if you are a doping athlete and you are planning to compete in London then you must withdraw from your Olympic team.
"Doping is cheating, plain and simple. And if you compete in London as a doped athlete then not only will you be cheating your fellow athletes, you will be cheating sports fans across the world, doing a disservice to your national flag and flouting the ideals of the Olympic Movement.
"A doping athlete cannot achieve success, it is a complete contradiction. Even if a doping athlete were to win a medal he or she would never be able to look at themselves in the mirror and say, 'Well done, I deserved this'."
London 2012 will be the most-tested Games in Olympic history with up to 6,250 urine samples analysed.
