The founding president of the World Anti-Doping Agency, Dick Pound, has criticised Novak Djokovic's claim that tennis is not affected by drugs cheats.

Djokovic told CNN at the Laureus World Sports Awards earlier this week: "As long as there is no proof that somebody is doping, the sport is clean."

Tennis was recently rocked by a drugs ban for Maria Sharapova, who tested positive for the recently prohibited substance Meldonium.

Asked if Djokovic's remarks were naive, Pound told STV: "Yes. That's a Lance Armstrong approach. 'I never tested positive therefore I am clean.' Wrong.

"I think it goes deeper than most people expect, and certainly deeper than they are prepared to acknowledge."

Djokovic's remarks followed criticism from Andy Murray last week, when the Scot spoke of his suspicion of some of his fellow professionals.

The British number one told the Mail on Sunday: "I have played against players and thought: They won't go away or they don't seem to be getting tired. Have I ever been suspicious of someone? Yeah. You hear things.

"It's harder to tell in our sport as people can make big improvements to a stroke or start serving better because they have made technical changes.

"If it's purely physical and you're watching someone playing six-hour matches over and over and showing no signs of being tired, you'd look at that."

Pound believes there are far more athletes doping than the current numbers suggest.

"Let's assume it's double digits and let's be really charitable and say it is only 10%," he said.

"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."

Asked if sport organisations, and their sponsors, should be doing more to clean up sport, Pound was clear that not enough is being done.

"A lot of the resistance we get comes from the sports organisations themselves who don't want to find people in their sport are using drugs because they think it reflects badly on them," he said.

"As far as the sponsors are concerned, I think they buy into sport because of the values.

"They should be looking more, could be looking more, to the organisations and say 'listen, we're putting in a lot of money to support this vision of sport that you have marketed to us. Now we want you to deliver it'."

Could sponsors coming together to insist more is done to eradicate doping be an effective approach?

"I think that's a very good scenario," he answered. "Whether you can get them that far or not is a matter of some doubt.

"But in the FIFA crisis, many of the main sponsors said 'you've got to sort this or we're going to have to rethink our involvement with you'."

Pound also rounded on football, saying there must be drugs cheats in the sport.

"There's no sport and no country that is without the risk," he said.

"If you look at the pace of football today, it's clear that some of these substances would be of enormous assistance.

"What they've done is simply allow this to go right over their heads. Does football have a problem? Yes. Does tennis have a problem? Yes. Every sport has a problem."

Pressed on why this hasn't played out in hard facts, Pound replied: "Because the people don't want it. They are resisting it. It is denial, denial, denial.

"The testing patterns have not been intelligent tests. If they've been directed, they've been directed at athletes that are known to be clean, or some that are expendable, because you have to come up with a few positive tests.

"There is a way forward. Not only because there is but because there should be. In the long run, there must be. We've got to solve this problem.

"You take them [drugs] not to level the playing field, no matter what anyone says. You take them to beat the other people.

"So if you are taking 20mg of whatever it is, and I find out, I don't take 20 to even with you. I take 40 because I want to beat you. So it escalates to the point you're getting toxic or even lethal dosages."