• Froome found to have an excessive level of an asthma drug at Vuelta
• Team Sky have ‘utmost confidence’ he stayed within permissible dose
• Rider says he was following team doctor’s advice after asthma got worse

Britain’s most successful road cyclist Chris Froome is fighting for his reputation after returning a failed drugs test during his victory in the Vuelta in September, a joint investigation by the Guardian and Le Monde can reveal.

Froome, who also won his fourth Tour de France in July, was found to have exceeded the permitted levels of the asthma drug salbutamol on a test taken on 7 September. Under World Anti-Doping Agency rules, riders are allowed a level of 1,000 nanograms per millilitre. However, the 32-year-old was found to have twice that in a urine sample taken during the Tour of Spain.

The Guardian understands lawyers and scientists are working on behalf of Froome and Team Sky to challenge the result, which is why it has not been made public until now. However, if the Briton is unable to offer a sufficient explanation for the abnormal finding or challenge the result itself he will forfeit his Vuelta title under the rules of cycling’s world governing body, the UCI.

If the test result is upheld Froome could face a significant ban, which may rule him out of next year’s Giro d’Italia and the Tour de France, where he was planning to go for a record-equalling fifth yellow jersey. In 2007 the Italian cyclist Alessandro Petacchi was given a 12-month ban for excessive salbutamol and stripped of his five stage victories in the Giro d’Italia.

Froome said: “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.”

Tweeting later on Wednesday, Froome added: “Thank you for all the messages of support this morning. I am confident that we will get to the bottom of this. Unfortunately I can’t share any more information than I already have until the enquiry is complete.”

Thank you for all the messages of support this morning. I am confident that we will get to the bottom of this. Unfortunately I can't share any more information than I already have until the enquiry is complete.

After a number of sources had told the Guardian and Le Monde about Froome’s adverse analytical finding, David Lappartient, the president of the UCI, confirmed his organisation was aware of it.

“There are rules of conduct,” Lappartient said. “I’m not here to break our rules. It’s not for me to interfere with this case. The procedure is secret, under discussion, and I don’t have any information on it. I do not even know in what stage [of the Vuelta] the sample was taken. I was just informed of an irregular test [result] but I don’t know whether [the taking of salbutamol] was justified or not.”

In a statement Team Sky said Froome received the notification of the adverse analytical finding from the UCI on 20 September, prior to the individual time trial event at the world championships.

The team principal, Sir Dave Brailsford, said: “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.”

What is salbutamol?

The UCI said in a statement that Froome is not facing a mandatory provisional suspension. It confirmed Froome was notified of an adverse analytical finding (AAF) on 20 September. The statement read: “The analysis of the B sample has confirmed the results of the rider’s A sample and the proceedings are being conducted in line with the UCI anti-doping rules.

“As a matter of principle, and while not required by the world anti-doping code, the UCI systematically reports potential anti-doping rule violations via its website when a mandatory provisional suspension applies.

“Pursuant to article 7.9.1. of the UCI anti-doping rules, the presence of a specified substance such as salbutamol in a sample does not result in the imposition of such mandatory provisional suspension against the rider.”

In September Froome spoke of his joy after becoming the first Briton to win the Vuelta, which also made him the first cyclist to win the Tour de France/Vuelta double in the same year since 1978. Later that month he also won a bronze medal in the world time trial championships in Norway – a result he described as “an amazing end to an unforgettable season”. But by then he had already taken a drug test, which threatens to damage his reputation as one of Britain’s most successful athletes.

That success had arrived late in Froome’s career. Until his mid 20s, his results were those of an average member of the peloton. However, the softly-spoken rider, who was born in Kenya but represents Britain, shot to prominence in 2011 with a second-place finish in the Vuelta. He explained his improvement had come about owing to the successful treatment of the parasitic flatworm bilharzia, which had robbed him of energy.

The following year he won an Olympic bronze medal in London before securing his first Tour de France title in 2013. Such as been his dominance since, he now enjoys a £4m-a-year salary from Team Sky – making him the best-paid rider in the world. Yet he has never experienced the same affection that another home rider, Sir Bradley Wiggins, has enjoyed with the British public.

Perhaps that has something to do with having never lived in England, having grown up in Kenya and South Africa and then lived in Monaco for many years. That said, he has been nominated again for Sunday’s BBC’s Sports Personality of the Year award, where he is third favourite behind the boxer Anthony Joshua and the Formula One driver Lewis Hamilton.

Inevitably, given cycling’s troubled past with doping, Froome has also faced questions over whether he is clean, despite having never returned an abnormal drug test result before now. Such has been the vitriol at times that at the 2015 Tour de France one fan spat at him while another threw a bottle of urine in his face. The way he carried himself at the time earned him plenty of admirers and Froome has always vehemently insisted he is no cheat.

Pointedly, when the Russian hackers Fancy Bears published documents showing that Wiggins had been granted therapeutic use exemptions for the powerful corticosteroid triamcinolone before three major races for a pollen allergy, Froome suggested his former colleague had been wrong. As Froome put it on his personal Twitter account last year, he was not prepared to “win at all costs”, adding “there are some athletes who not only abide by the rules that are in place, but also those of fair play”.

The test result is another blow for Team Sky, who have struggled to recover their reputation after an anti-doping investigation was launched into allegations about a package delivered to Wiggins at a race in 2011.

The UK Anti-Doping Agency closed its 14-month investigation in November after being unable to find sufficient evidence of wrongdoing. However, a second investigation by the digital, culture, media and sport select committee continues. Wiggins has always insisted that he is innocent and last month said his life was being made “a living hell” because of a “malicious witch-hunt” against him over the contents of the package.

That Froome is battling to clear his name will only further ramp up the pressure on Team Sky - which, after all, was built on the foundations of having a zero-tolerance drug policy.

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