American Lance Armstrong, currently holder of the leader's yellow jersey in the Tour de France, was totally exonerated by cycling's world governing body UCI yesterday, although it was admitted that he had shown minute traces of corticoids in a drugs test.

The UCI admitted that the Texan had taken a corticoid-based ointment to "treat a skin allergy" but said that his action conformed to the rules.

The UCI said: "The medical prescription was presented to the UCI. The rider was controlled on July 3rd after the prologue with a negative result, with no trace of corticoids.

"The rider was tested again on July 4th and then minimal levels were detected. The result of the analyses of these two days show that there was no systematic use."

It was explained that use of the ointment Cemalyt was authorised by the rules and "does not constitute the practice of doping."

At the time of the tests the UCI had said: "All riders tested after the first stage (on July 4th) were negative."

Earlier, UCI anti-doping supremo Leon Schattenberg said: "It is not excluded that traces of corticoids were found in the urine of Lance Armstrong."

Armstrong, who holds a six-minute lead with five stages remaining, has made a full recovery from testicular cancer over the past two years. The American has had to contend with a whispering campaign throughout the Tour - an event where constant revelations of doping since last year's Tour have led many observers to question the legitimacy of any outstanding performance.

Last week, Armstrong's doctor Lawrence Einhorn insisted the US Postal team rider was not taking any banned drugs. Quoted by French daily Le Monde, Einhorn said Armstrong was not having any medical treatment. "Like myself, he is a fervent supporter of the struggle against drugs. I can tell you he is only taking vitamins," Einhorn said.