Tour de France winner Alberto Contador has issued a statement that says he has always competed clean.
Contador has never failed a doping test and denies any wrongdoing
The Spaniard was linked to the Operation Puerto blood doping scandal but was cleared of wrongdoing.
"I've never committed a doping offence. I've never been involved in any act of doping. My promise against doping is absolute," he said in a statement.
"I am available to all authorities and will answer any questions, including providing my DNA."
Contador, who won this year's scandal-hit Tour by 23 seconds, said what should have been a celebration after his victory had turned sour because of the constant accusations and news coverage, which had forced him to have police protection.
"I have passed all controls, surprise and scheduled, in my house and at competitions, during racing and when not, of blood and urine," he added.
"I don't know what else I can say. I want to bring credibility to the new generation of cycling."
Operation Puerto was launched last year when police raids in Madrid and Zaragoza discovered quantities of anabolic steroids, blood transfusion equipment and more than 200 bags of blood.