The British athlete, her running battle over drugs, and a sport under a cloud of suspicion

The eyes of the athletics world would not normally have been trained upon the first heat of the women's 5,000 metres at the World Championships in Edmonton, Canada.

But the presence of one runner, Olga Yegorova of Russia, turned what should have been a low-key qualifying round into the target for an unprecedented display of anger at the continuing blight of drugs on the sport.

The British distance runner Paula Radcliffe held aloft a homemade banner which read "EPO cheats out", as Yegorova, who failed a test for the banned performance-enhancing drug last month but was controversially allowed to compete here on a technicality, qualified in second place for today's final.

Security officials threatened the captain of the British women's team with ejection from the stadium if she did not relinquish the sign, which she was holding up with team-mate Hayley Tullett, after the runners had completed two laps.

Radcliffe, 27, who finished fourth in the 10,000m two days earlier, was due to return home last night. But while she was the most visible part of the protest, she was not alone. A number of athletes running uneasily alongside Yegorova on Thursday night, including the British pair Kathy Butler and Hayley Yelling, wore red ribbons to mark what they saw as the continuing distortion of their sport through abuse of a substance.

Also competing with the Russian was Romania's Olympic champion Gabriela Szabo, who had threatened to boycott the race if Yegorova was allowed to take part but announced on the eve of the event that she did not want to give her opponent an easy ride. She gave the thumbs-up when she heard of Radcliffe's radical action. "It's good, it's good," she said. "For my heart, it is the best."

EPO, or to give it its full name, erythropoietin, artificially increases the number of oxygen-carrying red blood cells in the body, aiding endurance. It is a naturally produced hormone, but in recent years a synthetic version has been used by a wide range of sportsmen and women to increase their performance in the toughest events. Three years ago the Tour De France cycle race was suspended when widescale EPO abuse was detected. It is suspected that at least 20 cyclists have died as a result of strokes or heart attacks brought on by the thickening effect that injecting EPO has on the blood.

Rumours have circulated for years about the use in athletics of EPO, which remained undetectable until a test involving both blood and urine samples was introduced by the International Olympic Committee at Sydney last year.

The same test was deployed here by the International Association of Athletics Associations, which analysed samples from 30-40 middle distance athletes, including Radcliffe and Yegorova, in the week before the championships. Although one athlete yet to be named has tested positive for EPO as a result of that IAAF test, the other 10 whose blood samples warranted a follow-up urine analysis, including Yegorova, showed clear. The urine test can distinguish between natural and synthetic EPO, but it can only show up the presence of the latter if it has been taken in the three days preceding the test.

Yegorova, 29, has improved dramatically this season, beating Szabo three times after having lost to her by large margins in the past. Her positive test at the Golden League meeting in Paris, where she set the world's fastest time this year over 3,000m, was achieved through urine analysis, but officials neglected to take the necessary blood sample from her which would have corroborated the finding.

Embarrassed IAAF officials were forced to admit last Saturday that Yegorova could not be prevented from taking part in these championships, and when their own subsequent test on her established that she was not carrying EPO into the competition, the scene was set for angry protest.

Before these championships got underway, Radcliffe – whose strong feelings over the problem of EPO in middle-distance running caused her to pioneer the red ribbon protest at the 1999 World Championships in Seville – had criticised Yegorova's presence here. "When somebody has beaten you in two races this year, to see them flaunting it in your face, still thinking they are going to compete in the championships, is wrong," she said.

"It's not fair," she added after handing over her homemade sign. "Everyone watching that race knows Yegorova has failed an EPO test. She shouldn't be in the race and the girls shouldn't have to run against her. The British girls were thinking about what protest they should do. But they shouldn't have to protest – they've got to focus on their race. So we did our part and did the protest for them.

"She failed a test and got away on a technicality. We tried to make the banner as neutral as possible to get the point across rather than name her. It got on TV and has been reported so we hope we got the message across. I don't think Yegorova was aware of it although the Russian spectators were."

Radcliffe was harangued from the crowd at one point by Yegorova's husband. Other members of the Russian team called her "crazy". Butler, a former Canadian now competing for Britain, was disappointed the sign had been removed. "Apparently it's not a free country," she said. "I don't see why a sign saying that someone taking EPO should not compete should be taken away."

After finishing eighth, Butler said she would be very upset if she failed to reach the final by one place. That was exactly what happened as the other heat proved faster – it was actually won by Dong Yanmei, who was dropped from China's Olympic team last year amid suspicions of EPO abuse.

The controversy marks the latest clash of the war in athletics between the cheaters and the testers. Since Canada's Ben Johnson was stripped of the Olympic 100m gold medal in South Korea in 1988 after testing positive for the banned anabolic steroid stanozolol, battles have been waged with increasing urgency.

Doubts have persisted about the performances at the same Olympics of the American Florence Griffith-Joyner, who retired shortly after spectacular advances over 100m and 200m brought her two gold medals and world records that stand today. But Griffith-Joyner, who died in 1998, never tested positive.

Katrin Krabbe, Germany's 1991 world 100m champion, was banned for taking clenbuterol, an inhalant with anabolic effects. Last year's Olympics in Sydney saw another high-profile doping case in shot putter CJ Hunter, who was suspended after testing positive for another banned steroid, nandrolone.

Although Canada had another sprinter, Venolyn Clarke, banned here for taking the same drug as Johnson, the use of steroids, which bulk up athletes in power events and allow them to train harder, has increasingly given way to "smarter" methods of cheating less susceptible to detection.

Despite the glitch over Yegorova, the emergence of a reliable test for EPO marks a significant step for the drug-busters. The next involves developing the urine test so that a corroboration from blood samples is no longer required, and that should increase the ability of testers to investigate athletes on a random, short-notice basis.

Research is going on in Australia, Sweden and France to find a reliable test for human growth hormone, which has the effect of steroids but, being a naturally produced substance, remains undetectable. Science advances gradually, and the cheats move on. But, as the 5,000m protest demonstrated, the sport's administrators are coming under increasing pressure from the athletes themselves to ensure fair play.