Luxembourg's Frank Schleck says he will lodge a formal complaint for poisoning if analysis of his B sample confirms a positive banned substance test.
Schleck left the Tour late on Tuesday, hours after being told by the International Cycling Union (UCI) he had tested positive for Xipamide, a banned diuretic.
In a statement issued to Luxembourg radio RTL early on Wednesday morning, the Luxembourg star said he formally rejected that he had taken the banned substance.
"I categorically deny having taken any banned substances. I cannot explain the positive result of this test and I insist on my right to see the B sample analysed," said Schleck, who finished third overall in last year's race.
"If this analysis confirms the result of the first test, a formal complaint will be lodged for poisoning."
Although under UCI rules the 32-year-old Luxembourger could have started the race's 16th stage on Wednesday, RadioShack decided to send him home.
But team spokesperson Philippe Maertens said Schleck's reaction to the news was one of disbelief: "I saw his face when he heard the news ... he went very pale. It wasn't the face of someone who's guilty."
Schleck has four days in which to ask for the analysis of his B sample, which, if positive, will lead to his suspension from the team according to RadioShack, and a possible suspension from competition.
Because Xipamide falls under the 'Specified Substances' category of the World Anti Doping Code, Schleck has a chance to prove his innocence.
The code states that when an "athlete can establish that the use of such a specified substance was not intended to enhance sport performance, the period of ineligibility ... shall be replaced with the following".
For a first violation, athletes face anything from "a reprimand" to, at most, "one year's ineligibility".
Diuretics can be used to help riders lose weight, and therefore perform better in the tough mountain stages of the race.
More ominously, they can also conceal the presence of a banned drug by helping to flush it from the body through increased urination. Xipamide, a diuretic, is normally used for the treatment of oedema and hypertension. – AFP