Five-time Tour de France winner Eddy Merckx says he is taking Lance Armstrong's side in the row over doping claims made by L'Equipe.
The French newspaper alleges that signs of the blood-boosting drug EPO have been detected in samples of Armstrong's urine from the 1999 race.
Merckx told Le Monde newspaper: "Armstrong always told me that he never used doping products.
"Choosing between a journalist and Lance's word, I trust Armstrong."
Five-time Tour de France winner Miguel Indurain says the accusations against Armstrong are part of a campaign to discredit the American.
The Spaniard, who won the Tour five straight times between 1991-1995, also questioned the legality of claims against Armstrong.
"They have been out to get him in France for a number of years," Indurain told the website todociclismo.com.
"He's the one who knows about it, but it seems wrong that they are starting to dig over tests from years ago."
Armstrong has been plagued by accusations of drug abuse from elements of the French media since he won the first of his record seven Tour titles in 1999 after recovering from testicular cancer.
There were no tests for the drug then, but the paper claims samples have recently been re-tested by the specialist anti-doping laboratory outside Paris.
The Texan has always maintained he has never taken performance-enhancing drugs.
The International Cycling Union said there were no positive drug tests from the urine and blood samples taken on the 2005 Tour de France, when Armstrong took his seventh win.
Indurain added: "It's all very strange. I don't know to what extent it is legal to keep specimens like this.
"Anything about Armstrong is news these days, but the question is whether all this is true or not.
"There are question marks over the reliability of the test (for EPO) and there are a lot of doubts about the whole thing."
Germany's Jan Ullrich, the 1997 Tour winner who was also second three times to Armstrong, told German television: "I heard about it, but these are speculations so you can't really say anything about it.
"It's been six years, and, if it's true, I would of course be disappointed. But I can't say anything on it right now.
"Lance is the greatest of our time and maybe somebody's trying to put him down. I don't know what it's about, so all of this is very speculative."
Swiss Alex Zuelle, who finished second behind Armstrong in the 1999 Tour, said: "I won't say anything about it because my career as a professional is over.
"I'm not Armstrong. All of this is speculation. Sometimes they have proof, then they haven't ... I'm not interested in it anymore. For me, the Tour is over and done with; it's just too many years back."