Johaug's suspension for testing positive for anabolic steroid clostebol, while training in Italy in September 2015, had been due to expire on November 18.

But the FIS were hoping CAS would extend the Olympic gold medallist and seven-time world champion's ban as they claimed the 13-month suspension, handed down by the Norwegian Olympic and Paralympic Committee and Confederation of Sports' (NIF) Adjudication Committee, was too lenient.

It has now been increased to 18 months and will expire in April, which comes after the conclusion of the Pyeongchang 2018 Games scheduled to take place from February 9 to 25. 

Johaug has always denied wrongdoing and claimed to have used the banned substance inadvertently via a sun cream that was wrongly given to her by the team doctor.

Anti-Doping Norway argue she should be blamed for "not having undertaken further investigation of the drug she received and used", which reportedly came in a package marked with the word "doping".

They recommended a 14-month suspension before this was reduced by a month in the eventual NIF verdict.

The skier, who claimed she used the sun cream to treat cracked lips, insisted her doctor had given her the all-clear to apply it.

The case was handled by a Panel of CAS arbitrators with a hearing having been held at CAS headquarters in June. 

"Having reviewed the matter in full, the Panel noted that Ms Johaug failed to conduct a basic check of the packaging, which not only listed a prohibited substance as an ingredient but also included a clear doping cautionary warning," a CAS statement reads.

"Such omissions resulted in an anti-doping rule violation inconsistent with her otherwise clean anti-doping record.

"Nevertheless, in order to ensure equality in applying anti-doping rules, the Panel highlighted that it was obliged to apply a proportionate sanction, consistent with the level of fault. 

"For this reason, the Panel noted that, in such a situation of non-significant fault, the 2015 World Anti-Doping Code provides for a suspension range of between 12 to 24 months and determined in the present case that a period of ineligibility of 18 months, commencing on October 18, 2016, was appropriate."

Johaug was a member of Norway's winning 4x5 kilometres relay team at the 2010 Winter Olympics in Vancouver.

She won 30km silver and 10km bronze at Sochi 2014.

The Norwegian has also won the overall FIS World Cup title twice.

She triumphed in 2014 and 2016.