The President of the World Anti-Doping Agency, Dick Pound, has criticised Novak Djokovic for his comments about doping.
The world number one was speaking after he received the Sportsman of the Year award at the prestigious Laurens World Sports Awards earlier this week.
"As long as there is no proof that somebody is doping, the sport is clean," quipped the 11-time grand slam winner.
Pound took exception to this comment…
"That's a Lance Armstrong approach. 'I never tested positive therefore I am clean.' Wrong," said Pound told stv.tv.
"I think it goes deeper than most people expect, and certainly deeper than they are prepared to acknowledge."
Pound went on to say that the number of athletes doping in sport is much larger than feared and people need to realise this.
"Let's assume it's double digits and let's be really charitable and say it is only 10%," he added.
"Our level of positives is 2%. Why is the testing not more effective than that? The science is pretty robust and the system is good for whatever it does. It's the people that don't want it to work."