JOIN USHe told a doping conference convened by the World Sports Law Report at Twickenham rugby stadium that the criminal elements in illegal betting were also involved in steroid trafficking.
"My information is we now know the criminal underworld controls a significant proportion of world sport," he said.
He added that there was more money made in trafficking illegal performance-enhancing drugs than in dealing heroin.
Howman later told reporters his information came from law enforcement people "far more experienced and knowledgeable than any one of us".
"They say the underworld is involved in betting, in distributing steroids and it's the same jokers, it's not anybody new," he said. "I have been saying this for five or six years and now INTERPOL are justifying it. They now have the numbers and the information and they are really worried about it."
Howman also told the conference there was evidence that there had been attempts to bribe doping control officers.
He told reporters the amounts involved were "thousands of dollars".