Briton Froome won Saturday's eighth stage, a 195-km mountain ride from Castres, to lead overall by 51 seconds from Team Sky colleague Richie Porte with Spain's Alejandro Valverde in third place 1:25 off the pace.
His dominant performance was reminiscent of the way the disgraced rider Lance Armstrong would hammer the field in the first mountain stage of the Tour before controlling the rest of the race with often sterling performances in the time trials.
Asked to confirm his performances had nothing to do with banned substances, Froome said: "100 per cent. I think it's normal that people ask questions in cycling given the history of the sport.
"I know the sport has changed. There's absolutely no way I'd be able to get these results if the sport had not changed.
"Results now are definitely a lot more credible. The questions should be asked about people who were winning races maybe five, 10 years ago when we know doping was more prevalent."
While 2012 champion Bradley Wiggins last year lost his cool when grilled about doping and angrily hit out at accusations made on Twitter, Froome remained calm.
"For me it is a bit of a personal mission to show that the sport has changed," he said.
"I certainly know that the results I get are not going to be stripped 10, 20 years down the line. That's not going to happen."
Last year, American Armstrong was stripped of his seven Tour titles, won from 1999-2005, for doping and then admitted in a television interview in January he had taken performance-enhancing drugs.
Just as the translator finished saying Froome's words in French, the rider took the microphone again and continued: "Anyone who actually spends a bit of time with the team, with us... see that this is months and months of preparation - going to these training camps in altitude all together, the support off the bike from the sport staff, from my fiancée, this is so much preparation that it's not 'wow', it does add up."
- Sports & Recreation
- Lance Armstrong
- Alejandro Valverde
- Richie Porte