TENNIS: Greg Rusedski's failed drugs test: Greg Rusedski last night launched a remarkable defence against his positive drug test, claiming that tests on 47 of the world's top 120 tennis players had revealed elevated levels of the steroid nandrolone, and accusing the sport's governing body of covering up "one of the biggest scandals to surface in world sport".

In a statement through his lawyers, Rusedski professed his innocence and appeared to claim his positive sample was the fault of the Association of Tour Professionals, the governing body of the men's game.

Rusedski's claims, a day after he confirmed he had failed a test, raised serious questions about the ATP's administration of the men's game and its anti-doping regime.

The former British number one said the ATP had singled him out and reiterated that he believed he would be found innocent: "I will fight this case to the bitter end. I would like the ATP to drop this case as it is clear that the source of this problem is tennis rather than anything I did or took."

Rusedski's defence centres on the ATP's admission on July 9th last year that mineral supplements provided to leading players by ATP-approved coaches were responsible for "elevated levels" of nandrolone in 43 samples taken in the preceding 11 months.

Of the 43 samples, seven were "positive" - they had more than the legal threshold of two nanograms of nandrolone - but all seven players were eventually cleared of wilfully taking the substance.

According to Rusedski's statement, which he said details testimony from doping experts who examined the case, all these samples had the same "unique analytical fingerprint" and were from the same source.

Rusedski claimed his sample, taken on July 23rd, shared that fingerprint, as did three positive tests from as yet unnamed players.

"This type of analytical fingerprint has never been found in any other sport and therefore is unique to tennis. This indicates that the positives all spring from a common source," he said.

However, Rusedski has not supplied an explanation as to how his sample came to contain almost five nanograms of nandrolone, more than twice the legal limit.

A source close to Rusedski said: "The simple truth is he has not got the faintest idea how it got there. Everything he takes he has tested and it all shows negative for drugs. Nobody knows, but the ATP has got 47 samples with nandrolone in them and they are only acting against Greg."

Rusedski has hired a leading London PR firm, and his bold response is in part prompted by the adverse coverage his admission received in the British press. He has also retained Denton Wilde Sapte, the country's leading sports lawyers.

Rusedski's defence was criticised by Dick Pound, the chairman of the World Anti-Doping Agency (WADA).

"He's trying to get himself under the umbrella with the others. It's a strict liability offence: it's there and he has to account for it," said Pound.

The agency is conducting an independent investigation into how the ATP failed to prevent its sports medicine staff from routinely handing out supplements containing nandrolone between August 2002 and the following May.

Prof Ron Maughan, a world expert on nutritional supplements, said: "If Rusedski has been given anything by his trainers or taken a supplement himself then he's been extremely foolish. You cannot compete at Rusedski's level and be ignorant about the dangers of supplements."

WADA is backed by sports federations, the International Olympic Committee and more than 70 governments. Its aim is to establish uniform drug-testing regulations and sanctions across all sports and countries. It calls for two-year suspensions for first serious drug violations and life bans for a second. The code upholds the "strict liability" policy, meaning athletes are responsible for any banned substance in their body regardless of how it got there. If athletes can prove they were not at fault for a positive, suspensions can be reduced or waived.

Tennis has not, however, signed up to WADA and relies on three different bodies to police the sport. The International Tennis Federation takes care of drug testing at the grand slam tournaments and Davis Cup, the ATP deals with tests on the men's tour and the WTA with the women. When cheats have been caught the sentences have tended to be lenient; earlier this week Argentina's Mariano Puerta was given only a nine-month ban after testing positive for clenbuterol. Pound does not believe the sport is doing enough.

Yesterday Rusedski left Adelaide, Australia, where he had been competing in a warm-up tournament for the Australian Open, and flew to Sydney. He insisted he will play in the adidas International tournament beginning on Sunday, and he had no plans to withdraw from the Open, which starts in nine days in Melbourne.