Cheats are winning the battle against anti-doping authorities in elite sport, according to a top official.

David Howman, who chairs the Athletics Integrity Unit and served as director general of the World Anti-Doping Agency (Wada) for 13 years, says the anti-doping system has "stalled", allowing those who take banned substances to prosper.

"Let's be honest and pragmatic – the system has stalled," Howman said.

"Intentional dopers at elite level are evading detection. We are not effective enough nowadays in catching cheats.

"Our ineffectiveness in dealing with those who are beating the rules is hurting the anti-doping movement's credibility."

Former world 100m silver medallist Marvin Bracy-Williams was banned for more than three and half years last month after admitting doping offences, while fellow American Erriyon Knighton was banned for four years in September after testing positive for steroids.

Women's marathon world record holder Ruth Chepngetich was banned for three years in October after her sample showed a banned diuretic commonly used as a masking agent.

The unity of world anti-doping effort has been compromised in recent years.

Wada and the US anti-doping agency have clashed over the handling of a doping scandal involving 23 Chinese swimmers, funding and the staging of next year's Enhanced Games, an event which encourages the use of banned substances, in Las Vegas.

The anti-doping authorities in Kenya, whose athletes have been involved in a spate of positive tests, are on a Wada watchlist, while Russia, whose officials were found to be involved in the systematic cheating and swapping of samples at the 2014 Winter Olympics at Sochi,, external are still judged as "non-compliant" by Wada.

Howman suggested better sharing of information among anti-doping bodies and a "bounty-hunting" style incentivisation to encourage them to proactively chase cheats.

"We must all do better to support our clean athletes by catching the dirty ones, especially those at the pinnacle of sport," he added.

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