If he fails to provide a satisfactory answer, cycling's governing body the UCI is likely to proceed with an anti-doping rule violation case which could strip him of his Vuelta victory and see him miss a large chunk of next season.

Speaking to Press Association Sport, Professor Chris Cooper said Froome "would have to be really stupid" to try to cheat with Salbutamol as it has no performance-enhancing effects when taken via an inhaler and he would have known he was being tested every day.

The Team Sky leader has made no secret of his use of Salbutamol throughout his career and he even notes it on his doping control forms.

Under World Anti-Doping Agency (WADA) rules, athletes with asthma can take up to 16 normal doses of the drug (100 micrograms) via an inhaler every 24 hours but no more than eight in a 12-hour window.

This translates to an allowed concentration of Salbutamol in a urine sample of 1,000 nanograms per millilitre. Froome was tested 21 times during La Vuelta but on September 7, after the 18th stage, his sample was double the permitted amount.

Mr Cooper, who runs the University of Essex's Centre for Sports and Exercise Science, said Froome and Team Sky are likely to have requested all of his other samples to find out if he was close to the limit on those days, too, as he has admitted that he upped his dosage, on his doctor's advice, to treat his worsening symptoms.

As everyone excretes and metabolises the drug in a slightly different way, Froome may be able to prove that the adverse finding is a result of his physiology and the unusual circumstances of riding a three-week bike race. To do this, he is likely to be tested in a laboratory.

"I'm sure Team Sky have been trying to do this already but it's not easy to replicate La Vuelta," explained Mr Cooper.

"Sure, you can replicate some of the variables - dehydration, for example - to get you in the ball park, but it's not going to be the same."

The University of Kent's Dr John Dickinson - who has tested numerous British Olympians for asthma, including Team Sky riders - agrees with Professor Cooper on Froome's likely approach.

Dr Dickinson said: "Some individuals may have a greater metabolism and excretion rate that may cause the Salbutamol concentration to be increased.

"The World Anti-Doping Agency are aware of this and they will ask any athlete with adverse levels to provide evidence to explain why."

As well as dehydration, it is possible that what Froome was eating that day may have played a part or if he was any other medication.

Dr Dickinson also agrees that the research on the possible benefits from inhaled Salbutamol are clear: it is not a performance-enhancing drug but it is performance-enabling for asthmatics.

There is, however, evidence to suggest that it does provide a competitive benefit if taken intravenously or in tablet form.

Update 12.25pm: British cyclist Chris Froome could miss most of next season after a urine sample he gave at this year’s La Vuelta was found to contain twice the permitted concentration of asthma drug Salbutamol.

The 32-year-old Team Sky rider may also lose his victory in that race - the first by a British cyclist - and be unable to defend his Tour de France title next July or attempt to win a third straight Grand Tour title at the Giro d’Italia in May.

The adverse analytical finding occurred in a routine test after the Vuelta’s 18th stage on September 7 - a day that saw Froome respond to a disappointing ride the day before by stretching his lead over rival Vincenzo Nibali on the last climb.

Conducted by the Cycling Anti-Doping Foundation, the independent body set up by the International Cycling Union (UCI), the test found the concentration of Salbutamol in Froome’s urine sample was 2,000 nanograms per millilitre (ng/mL), double the World Anti-Doping Agency’s (WADA) limit of 1,000 ng/mL.

Salbutamol, which is also marketed as Ventolin, is widely used by asthma sufferers, most commonly in an inhaler, to relax the muscles in the airway.

A member of the beta-2 agonist family of drugs, Salbutamol is banned by WADA when taken intravenously or in pill form - as research suggests large doses administered like this can boost performance - but asthma sufferers are allowed to take up 1,600 micrograms over 24 hours, without exceeding 800 micrograms (mcg) every 12 hours. A typical dosage, or puff, is 100 mcg.

In a statement issued by Team Sky, 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."

Froome, who records his Salbutamol use on his doping control forms, was informed of the adverse finding on September 20, the day he capped a stunning season with a bronze-medal ride in the time trial at the Road World Championships.

In a statement, the UCI said Froome’s B sample - athletes’ anti-doping samples are split into A and B samples as a fail-safe precaution - had been analysed and it confirmed the results of the initial test. The Swiss-based body added that under its rules Froome is not subject to a mandatory suspension.

The next stage in the process will be for Froome and Team Sky to come up with a scientifically-backed explanation for why the September 7 sample contained too much Salbutamol and the 20 other tests he gave during the race did not.

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."

The debate will focus on when Froome took his last dose of the drug, how dehydrated he was and if anything else he was taking or eating may have had an impact.

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.

— Chris Froome (@chrisfroome) December 13, 2017

There are several precedents, though, for what might happen next, as Italian rider Alessandro Petacchi was eventually given a one-year ban for taking too many puffs at the 2007 Giro. He was also stripped of the five stages he won - his Salbutamol concentration was 1,320 ng/mL.

Leonardo Piepoli returned a sample with an even higher concentration of the drug than his compatriot Petacchi on the same day but was not banned as he was registered in Monaco, whose cycling authorities chose not to pursue the matter.

But a third Italian rider, Diego Ulissi, was given a nine-month ban in January 2015 after a sample he gave at the previous year’s Giro was found to contain a similar amount of Salbutamol as Froome’s.

Ulissi’s attempts to explain the reading included trying to replicate the conditions of the day he was tested in a lab - something the UCI is likely to insist of Froome, too.

In the meantime, the Kenyan-born rider and his British team will try to continue as normal but there is no escaping the fact that this is a crisis, particularly as it comes so soon after the controversy surrounding the delivery of a mystery package to Team Sky’s former leader Sir Bradley Wiggins at a race in 2011.

That saga resulted in a long and damaging UK Anti-Doping investigation which was unable to either prove or disprove there had been any wrongdoing.

Froome played no part in that episode but now finds himself facing a ban that could cost him one of his greatest wins, a shot at joining cycling’s greats next year and his standing within the sport and wider public.