French newspaper Le Monde said the British cyclist could not sign on for the 2018 edition of the famous Grand Tour as race organisers the Amaury Sport Organisation (ASO) continue their bid to stop him competing.

Froome is the defending champion with this year's Tour beginning on Saturday (July 7).

But the rider, who completed his hat-trick of Grand Tours after winning the Giro D'Italia this year, has been embroiled in controversy after he failed a drugs test while winning the 2017 Vuelta a España.

Any wrongdoing has been denied by Froome who has pledged to clear his name, but the case is not resolved.

Reports first emerged in March that ASO had "no intention of letting a rider race with a potential anti-doping violation hanging over him".

ASO, it was reported, believed they could win any legal challenge from Froome's Team Sky outfit due to their rules about safeguarding the image of the race. 

Team Sky will now appeal the latest stumbling block against them to the Court of Arbitration run by the French Olympic Committee, according to Le Monde.

A Team Sky spokesman also told The Guardian: "We are confident that Chris will be riding the Tour as we know he has done nothing wrong."

Froome tested positive for asthma medication salbutamol at the 2017 Vuelta.

He was found to have had twice the permitted 1,000 nanograms per millilitre concentration in his sample but was not suspended.

The Briton would equal the record number of Tour de France victories should he win the race again.

His victory at this year's Giro came after a sensational ride on the 19th stage, when he launched a stunning solo breakaway 80 kilometres from the finish at Monte Jafferau to snatch the leader's pink jersey.

He is just the third man to hold all three of cycling's Grand Tour titles at the same time.