Team Sky said in a statement that Froome experienced "acute asthma symptoms" during the final week of the Vuelta and increased his dosage of Salbutamol, within permissible limits, on doctor's advice.

The four-time Tour de France winner conducted a urine test on September 7 which revealed a concentration of Salbutamol of 2,000 nanograms, twice the WADA threshold of 1,000.

The Team Sky statement said the "use of permissible dosages of Salbutamol can sometimes result in elevated urinary concentrations, which require explanation".

Froome took victory in this year's Vuelta a Espana but if he is unable to explain the excess levels of Salbutamol in his body he could potentially face a ban and lose his title.

But the 32-year-old has vowed to provide the UCI with whatever they need for their investigation.

“It is well known that I have asthma and I know exactly what the rules are. I use an inhaler to manage my symptoms (always within the permissible limits) and I know for sure that I will be tested every day I wear the race leader’s jersey.

“My asthma got worse at the Vuelta so I followed the team doctor’s advice to increase my Salbutamol dosage. As always, I took the greatest care to ensure that I did not use more than the permissible dose.

“I take my leadership position in my sport very seriously. The UCI is absolutely right to examine test results and, together with the team, I will provide whatever information it requires.”

Team Principal Sir Dave Brailsford added: “There are complex medical and physiological issues which affect the metabolism and excretion of Salbutamol. We’re committed to establishing the facts and understanding exactly what happened on this occasion.

“I have the utmost confidence that Chris followed the medical guidance in managing his asthma symptoms, staying within the permissible dose for Salbutamol. Of course, we will do whatever we can to help address these questions.”