"No, I never had any sense that Cadel Evans was doping," he says. "My belief in the Tour has been restored to a degree in that I think it's now possible to win the Tour de France clean.
"If somebody said, 'when did the cut-off point come and when did you start to believe it was possible?', it was that 2011 tour. That was a more human tour.
"I'm not saying for certain that the last five tours have been won by clean riders but my view is that they were clean."
Walsh gives no credence to accusations that Froome was doping when he won for the second time last year.
"People say Chris Froome has done the Col de la Madone, Lance's famous training mountain near Nice, faster than Lance. Well, [Australian rider] Richie Porte does it much faster than Froome. Does that mean Richie Porte is doping? No, it doesn't.
"The sport changes. These guys get lighter. On a climb like that, of course they can beat times previously.
"There are Australian swimmers who have set new world records that were previously held by Chinese swimmers. Does that mean the Australians were doping? No it doesn't. It's entirely natural that times are going to improve and the one who sets the new mark is not doping, even if the one who set the old mark was."