The criminal underworld now controls a large proportion of world sport, according to World Anti-Doping Agency director general, New Zealander David Howman.
Howman has told a doping conference in London that criminal elements in illegal betting are also involved in steroid trafficking.
Howman says more money can be made in trafficking illegal performance-enhancing drugs than in dealing heroin.
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Howman also told the conference there was evidence there had been attempts to bribe doping control officers.