As a result the Norwegian, one of the superstar names in cross-country skiing, has lost the overall World Cup and Tour de Ski titles he claimed in the 2014-15 season.

His ban comes after a successful appeal made by the World Anti-Doping Agency (WADA) to the Court of Arbitration for Sport (CAS), which has opted to quash an International Ski Federation (FIS) verdict which cleared the 31-year-old of blame.

Sundby tested positive for endurance booster salbutamol on both December 13, 2014 and January 8, 2015.

The substance is allowed in excess of limits - to a certain amount - if an athlete can prove the high levels are due to a required therapeutic, but Sundby crucially used a nebuliser to inhale his asthma medication.

This requires a higher labelled dosage than a handheld metric dose inhaler, and pushed the Norwegian, who has suffered from asthma since childhood, over the allowed maximum dose.

The FIS Doping Panel found that the athlete had not committed an anti-doping rule violation for using a nebuliser but the CAS backed up WADA's appeal and said the method a substance is taken is important.

"The arbitration centered on the athlete’s administration of his asthma medication, salbutamol, with the use of a nebuliser," a CAS statement said.

"In its decision, the CAS Panel found that the method of ingestion (i.e. inhalation) must be distinguished from other forms of administration such as ingestion or injection, and that the dosage allowed under the FIS Anti-Doping Regulations must be understood as the prescribed “labelled” dosage.

"Any use of salbutamol with a nebuliser beyond such “labelled” dose, without a therapeutic use exemption constituted an anti-doping rule violation."

Sundby's degree of fault is "light", the CAS said with his ban beginning from July 11 of this year - meaning he will not miss any competitions.

He was given the nebuliser by a team doctor, with the FIS claiming that using the device outside of a hospital was "questionable".

"FIS fully shares the view of the CAS that Martin Johnsrud Sundby is not to be considered as an intentional doping offender but that his sanctions result from the strict application of the anti-doping rules and the WADA Prohibited List as a consequence of his reliance on questionable medical advice to administer salbutamol outside a hospital," the FIS said.

Sundby's results at the FIS Cross-Country World Cups in Davos, Switzerland, on December 13, 2014, and in Tolbach, Italy, on January 8, 2015, have been annulled.

He won over 15 kilometres in Davos and was third in a 35km race in Tolbach - with the latter forming part of the Tour de Ski, a series of races which forms a separate competition but also counts to the overall World Cup standings.

The FIS has stripped Sundby of the 143 points he claimed at both races, as well as the 400 he received for winning the Tour de Ski outright.

His results in the Tour de Ski races after Tolbach have also been declared void.

As a result he has slipped to sixth in the overall standings, with Switzerland's Dario Cologna now promoted to champion.

Another Norwegian, Petter Northug, is the new 2014-15 Tour de Ski winner.

Sundby, who will also forfeit prize money, defended both of the titles he has now lost during last season, the 2015-16 campaign.

A Norwegian Ski Association statement said: "This is a judgment that is not about having achieved advantages in competition, but on how our doctors have understood unclear technical regulations on how a legal medicine can be taken. 

"Martin has not achieved competitive advantages by following doctors' orders."