Tennis must guard against doping even if performance enhancing drugs have not been a major problem in the sport, former world number four Tim Henman warned.

“People have cheated, we’ve had positive drugs tests in tennis and we’ve got to be absolutely at the forefront of testing to make sure that the deterrent is great enough to put people off,” the Briton said.

High-profile men’s players Marin Cilic of Croatia and Serbia’s Viktor Troicki both fell foul of anti-doping regulations last year.

Cilic served a four-month ban for taking a banned stimulant while Troicki is still off the Tour after his 18-month ban for failing to provide a blood sample was cut to 12.

The International Tennis Federation (ITF) is introducing a biological passport system, following calls for more anti-doping procedures from leading players like Roger Federer, but Henman doubts whether doping can even help tennis players.

“It’s a very physically demanding sport but I still classify it as a skill sport. If you’ve got a very bad backhand, it doesn’t matter what you’re going to take, it’s not going to get better,” he said.

“But we’ve got to make sure the testing is often, and out of competition testing is very important to make sure we have a clean sport.

“Because to our audience it has to be a level-playing field.”