Tour de France winner Floyd Landis has hit back at criticism of him by World Anti-Doping Agency chief Dick Pound.
Landis has denied taking performance-enhancing drugs
Pound described Landis' stage 17 win, after which he tested positive, "as a great story", adding, "but if it seems too good to be true, it probably is.
"He was 11 minutes behind, and all of a sudden there's this Herculean effort, where he's going up mountains like he's on a goddam Harley."
Landis has responded by calling Pound's comments "defamatory and absurd".
"Mr Pound should conduct himself in a manner consistent with the seriousness of the unsubstantiated allegations against me and the damage they have caused to a great number of people," he added in a statement.
Landis, who claims his positive test for testosterone was due to flawed analysis by a French laboratory, could be the first Tour winner to be stripped of his title if he is found guilty of taking prohibited drugs.
He claimed his "livelihood and family have already been unfairly and severely damaged" and accused anti-doping agencies of "routinely ignoring their own rules without regard for fairness or ethics."
"Mr Pound's published reference to the testosterone in my system proves he has not even bothered to review the facts regarding the unsubstantiated allegations against me," Landis added.
"My testosterone levels were tested as normal following stage 17 of the 2006 Tour de France and this fact is clear to anyone who cares to review the lab data."