The drug trap: Former gold medallist Darren Campbell warns that failed drugs tests may be caused by companies catering for body-builders

Tyson Gay (left) and Asafa Powell may well have unwittingly taken contaminated products (AFP)

British athletes heading to Moscow for the World Championships next weekend are risking a similar fate to the absentee star sprinters Asafa Powell and Tyson Gay if they are taking dietary supplements, some of which may have been contaminated by products designed for body-builders.

There is a growing concern that substances used in body-building, where there is no official testing for performance-enhancing drugs, have infiltrated supplements taken by other athletes unaware of their illegality. Britain's former Olympic gold and silver medallist sprinter Darren Campbell is among those who accept that the claims made by Jamaica's Powell and American Gay that their failed tests were due to unknowingly taking contaminated substances given by their advisers may have some merit.

He believes that products which are intended for body-builders are increasingly available in over-the-counter or online supplements in a guise which makes them appear legitimate. "The biggest problem is some companies who make legal products for sports people also make illegal products for the body- building market. So what Powell and Gay are saying is quite feasible. I think there is a good chance they are telling the truth."

The 39-year-old Campbell, now a Sky TV presenter and sprint coach to newly promoted Premier League club Cardiff City, has inside knowledge of the supplement industry. For seven years he has run a sports nutrient business with John Williams, nutritionist to the Welsh rugby team and British Lions. They also supply dietary products to 18 Premier League football clubs and the world champion boxer Nathan Cleverly.

"We thoroughly test all the original ingredients, some of which may come from China and Europe, before they are blended and manufactured," Campbell says. "Then the finished product is again checked by a company in Cambridge who do the official tests for the sports organisations. The big companies like Maximuscle will get their products tested by them.

"The public need to understand the difference between performance-enhancing drugs and nutrient products. We only source our products from companies that do not make illegal substances but I suspect there are some that don't."

Campbell's belief that the use of contaminated supplements is a major problem is endorsed by the pole-vault legend Sergey Bubka, now a candidate for the presidency of the International Olympic Committee. The Ukrainian told The Independent on Sunday that his advice to athletes is: stop taking tablets. "The supplement industry has become a huge multi-million dollar business and the athletes are not protected. We advise and educate them but in the end it is their responsibility what goes into their bodies.

"There is enough information available to avoid this sort of thing, but the answer is simple: don't use them. Just take regular vitamins. A lot of these supplements are manufactured in the United States where there is no longer a requirement to provide clear information about what is contained in the tablet.

"When a small factory produces substances, they can include some medicines that contain steroids. They may try to wash them out but they do not clean very well and instead they contaminate. Who pays the price? The athlete."

Ian Musgrave, senior lecturer in pharmacology at the University of Adelaide, says that Powell's defence of "never knowingly" taking drugs is a "very real possibility" and that contamination is widespread. One report found 70 per cent of weight-loss supplements contained ingredients not listed on the label.

Powell's test revealed a synthetic stimulant, oxilofrine, used as a fat-burner which, as a natural product, is found in extracts of bitter orange. This was also the substance used by a number of positively tested British boxers, including the former WBA world middleweight champion Brian Magee, who served a six-month suspension. He escaped the customary two-year ban because he showed the substance was an unlabelled ingredient in a sports supplement designed for body-builders.

Michele Verroken, the former UK Sport anti-doping chief who now runs the advisory organisation Sporting Integrity, says the supplement controversy is not a new phenomenon. "If you think back to 1998-99 when we had all those nandrolone positives, it's exactly the same scenario," she says. "The supplement market remains unregulated to the same level you have with licensed medicine. The question is whether industry-led standards are as comprehensive as they need to be to prevent contamination which may be accidental or even deliberate."

Campbell, a vehement anti-drugs campaigner, says a time he spent away from athletics trying to make a career as a footballer was spurred by attempts by "certain individuals" to draw him into a drugs programme. Now he warns the goalposts have shifted, and that athletes are in danger of becoming unwitting victims of rogue manufacturers whose products may seriously harm their health. "These people don't care about the welfare of athletes. For them, it's just about making money."

Darren Campbell will present Game Changers, a new Saturday morning children's show live on Sky Sports from 17 August

The dope sheet

30 April 2013 Russia's European 800m champion Yelena Arzhakova banned for two years after her biological passport is deemed abnormal; the Olympic silver medal discus thrower Darya Pishchalnikova is banned for 10 years for a second positive test.

13 June Jamaica's 400m runner Dominique Blake banned for six years after testing positive for banned substances on two separate occasions.

15 June Fellow Jamaican Veronica Campbell-Brown, the three-times Olympic gold medallist, is found to have tested positive for a banned diuretic in May.

14 July Sprinters Asafa Powell and Sherone Simpson of Jamaica test positive for banned substances including oxilofrine and the American 4x100m Olympic silver medallist Tyson Gay for an unidentified substance. Reports also claim three other Jamaicans could be implicated.

15 July Another Jamaican, discus thrower Allison Randall, confirms that she will serve a ban for doping. Police in Italy search the hotel rooms of Powell and Simpson for drugs.

16 July Powell's manager, Paul Doyle, claims the sprinter had become reliant on substances given to him by his trainer.

17 July Powell and Simpson's trainer, Chris Xuereb, argues: "Although I suggested certain vitamins to these athletes, it is ultimately the athlete's responsibility to accept or reject my suggestion."

19 July Jamaican discus thrower Traves Smikle tests positive.

31 July Nine Turkish athletes are banned for two years for using anabolic steroids.

Grace Mennem