Updated - Contador's management threaten to sue media after latest doping allegations

Alberto Contador’s management team has reiterated that clenbuterol entered his body via contaminated meat and has threatened to sue any media organisation that says otherwise.

Their aggressive stance has been prompted, in part at least, by an article on the Belgian magazine Humo’s website in which a detailed description of Contador’s alleged blood doping practices is provided by an anonymous source who claims to be “close” to the Astana team. The full article is due to appear in the magazine on October 12 but the extract published on the website has already been widely disseminated.

The question-and-answer style article makes for explosive reading, providing an explanation for how and why an athlete could suddenly test positive for traces of both clenbuterol and plasticizers.

“He had a blood withdrawal after the Dauphiné Libéré, and in that blood there still remained a trace of clenbuterol,” the source - who is not a rider - unequivocally tells Humo.

 “At the Dauphiné, Contador was still a touch overweight and clenbuterol is used to remove the last kilo or two without diminishing muscle mass, or, in the best case, increasing it slightly,” said the source.

“During the period after the Dauphiné, Contador removed small quantities of blood so as not to alter the values in his biological passport. This occurred when there were still traces of clenbuterol in his blood and they remained there until transfused back into his body.”

The insider says this explains why the athlete tested negative for the drug until the rest day when the transfusion was carried out.

The article also quotes a different source,  a rider who is not part of the Astana team. The rider tells the publication that clenbuterol – which can increase the metabolic rate and therefore speed up fat-burning – is used in conjunction with the thyroid hormone Triiodothyronine, also known as T3, which accelerates the breakdown of fatty tissue. This combination means that smaller quantities of clenbuterol are required to achieve the desired results.

In the article, the Astana insider claims that blood doping still occurs in the peloton but says the advent of the biological passport has meant that instead of two or three blood transfusions of 400 – 500cc each during a race, now the amounts are more in the region of 150cc so as not to show up as sudden fluctuations in blood values.

Responding to the allegation, Contador's press agent, Jacinto Vidarte, said: "Contador vigorously denies the veracity of the information published by some media and reaffirms his innocence, as proved by all scientific reports provided to the UCI that were made available to the public, and as confirmed by his biological passport."

"The legal team of Alberto Contador will take legal action against defamatory information published so far by various media and websites, due to their absolute lack of veracity," added Vidarte.