Lance Armstrong has been accused of using performance-boosting drugs in a series of detailed emails sent by his former team-mate, Floyd Landis.
Landis — stripped of his 2006 Tour de France title after failing a dope test — sent emails to cycling officials and sponsors finally admitting the offence, according to The Wall Street Journal.
Armstrong has always denied doping and has never tested positive or been sanctioned by the cycling authorities.
Pat McQuaid, the head of cycling's governing body UCI, questioned Landis's credibility. McQuaid said Landis holds a “grudge” against Armstrong and others.
The newspaper said Landis’s emails detailed his own systematic use of performance-enhancing drugs. In an interview on Wednesday, Landis admitted using drugs during his career. “I want to clear my conscience,” the 34-year-old said. Landis alleged that during his career, he and other American riders learned how to conduct blood transfusions, take the synthetic blood booster Erythropoietin (EPO), and use steroids.
The Wall Street Journal said it had seen three emails sent earlier this year. “Mr Landis copied seven people on these three emails, including officials with USA Cycling and the International Cycling Union,” it said.
Landis, the first rider to be stripped of a Tour victory, previously denied any wrongdoing but the Court of Arbitration for Sport rejected his assertion.
In February, a French judge issued an arrest warrant against him on suspicion of hacking into an anti-doping laboratory computer.
The head of the French anti-doping agency, Pierre Bordry, said the judge believed Landis wanted to prove the laboratory where his samples were tested was wrong.