American Floyd Landis became the latest casualty in the war against doping after a second drugs sample confirmed a positive test for excessive amounts of the male sex hormone testosterone on the Tour de France.
The American is now likely to become the first winner of the world's most famous cycling race to lose his title because of a positive dope test and he also faces a two-year ban.
A statement issued by the International Cycling Union (UCI) on Saturday said Landis's B sample taken after his win in the 17th stage on July 20 had confirmed a doping offence.
"For us, he cannot be the Tour de France winner anymore," Tour de France director Christian Prudhomme told Reuters from his holiday residence. "Technically we cannot say he has lost his title but he has soiled the yellow jersey."
Landis, who again denied ever taking drugs, was immediately sacked by his Swiss team Phonak.
"Landis will be dismissed without notice for violating the team's internal Code of Ethics," Phonak said in a statement.
"Landis will continue to have legal options to contest the findings. However, this will be his personal affair and the Phonak team will no longer be involved in that."
His Phonak team mate Bert Grabsch added: "This is a catastrophe and huge disappointment for me and the whole team."
In a statement on his Web site the 30-year-old American said he had never taken a banned substance.
"I have never taken any banned substance, including testosterone. I was the strongest man in the Tour de France, and that is why I am the champion," Landis said.
"I will fight these charges with the same determination and intensity that I bring to my training and racing. It is now my goal to clear my name and restore what I worked so hard to achieve."
His lawyer Howard Jacobs said he was waiting to receive full laboratory documentation for the B test.
"In consultation with some of the leading medical and scientific experts, we will prove that Floyd Landis's victory in the 2006 Tour de France was not aided in any respect by the use of any banned substances," Jacobs said.
Landis and Jacobs will also question the UCI's premature release of the A sample findings and the anonymous leak of the carbon-isotope test results to the New York Times on July 31, the statement said.
The UCI statement said an analysis of the B sample confirmed the result of an adverse analytical finding notified by the anti-doping laboratory of Paris on July 26.
"In accordance to the anti-doping rules, the Anti-Doping Commission of the UCI will request that the USA Cycling Federation open a disciplinary procedure against the rider."
Spaniard Oscar Pereiro Sio, who finished second 57 seconds adrift of Landis in the overall standings, is now likely to be declared the winner of the race. "Today is another step forward but I don't know what the UCI's decision is yet, or what Floyd's defence is going to be," Pereiro told Spanish state television.
Pereiro, who is due to give a news conference in Vigo at 1600 GMT, would then become the first Spaniard to win the Tour since Miguel Indurain's last victory in 1995.
Landis, 30, tested positive for testosterone after an astounding comeback in the last mountain stage. It came just a day after a very poor performance which all but knocked him out of contention.
Landis now has 10 days to respond to the documents that are provided, according to U.S Anti-Doping Agency (USADA) rules.