Tour de France: Critics wrong to accuse Chris Froome of doping, says reporter David Walsh

Chris Froome doesn't deserve to be accused of winning the Tour de France by doping, according to the journalist who helped expose Lance Armstrong as a drug cheat.

Team Sky rider Froome has almost guaranteed victory in the 100th Tour de France after finishing Saturday's stage 20 to Annecy-Semnoz with a lead of more than five minutes.

With only Sunday's processional stage into Paris to go, Froome will be the second British winner in as many years following on from Team Sky team-mate Bradley Wiggins's 2012 success.

Kenya-born Froome's remarkably dominant display throughout the Tour has prompted some critics to suspect the 28-year-old of doping to enhance his performance.

But Sunday Times reporter David Walsh, who played a significant role in unearthing American rider Armstrong's long history of doping, has spent several weeks inside the Team Sky camp and he is adamant Froome shouldn't have to defend himself from drug slurs.

Walsh spoke to Richard Freeman, one of Team Sky's doctors, about Froome's dramatic improvement in the 2011 Vuelta a Espana and was convinced by the medical expert's theory.

"I was confused because Chris hadn't performed with this consistency for the team and I wondered how he'd done it," Freeman told Walsh.

"Before I could be satisfied, I spent two weeks re-examining all of his blood samples from his two seasons in our team and looked at all the information in his biological passport.

"What I wanted was to compare blood results from the Vuelta with the blood tests he'd done previously to see if there were changes. There weren't.

"His blood values remained the same and whatever the reasons for him riding consistently in that Vuelta, in my opinion it wasn't down to him doing things he shouldn't have done."

Team Sky chief Davis Brailsford told Walsh that he thinks Froome's progress in 2011 was in part related to his successfully managing his bilharzia, a debilitating condition caused by a parasite that attacks red blood cells.

Walsh also quizzed Sky's chief doctor, Alan Farrell, about therapeutic use exemptions (TUEs) which have been one route taken by cyclists seeking unethical advantages.

They claim a medical reason for needing a banned corticosteroid, persuade the team doctor to apply for it and try to beat the system that way.

But Farrell told Walsh: "I've been with the team since April last year, almost 16 months. Applications for TUEs come from me and in my time, we have applied for two TUEs."