Chris Froome believes that cycling's code of omerta, which sheltered dopers in the peleton for decades, has been broken and that the sport is cleaner than it has been for more than 20 years.

The Team Sky rider, who will be a strong favourite for the Tour de France when it starts on Saturday, insists he has reached the top without resorting to chemical assistance. But he says he understands why many remain sceptical about the extent of drug use in the sport, especially following Usada's forensic dissection of Lance Armstrong's doping last year.

"Cycling is in probably the best place it has been in the last 20-30 years," he said. "The revelations about Lance have given us the opportunity to show people that the sport has changed."

Froome also described as "really sad" a suggestion in the recent publication Not Normal? – by the French journalist and former Festina trainer Antoine Vayer – that there may be suspicions surrounding him.

Vayer analysed the watts generated by 21 riders on iconic mountain stages and concluded that climbs by Marco Pantani and Lance Armstrong had been "mutant", or highly suspicious, while Froome's effort was merely "miraculous", indicating possible suspicions.

Froome's response was measured, if exasperated. "It is hard not to get angry because it almost feels the better we do our job the more people think we're doping," he said. "There is still a lot of scepticism out there and a lot of fans have been let down. I sympathise with that. I am one of those fans. But the sport has changed. I know that my results aren't going to be stripped in five, six, seven years' time."

During last year's Tour Bradley Wiggins was riled by a steady battery of questions about doping. And Froome is preparing to face a similar grilling.

"I'm expecting to have to answer questions about doping," he admitted. "But personally I'm really confident the races I've done building up to the Tour, being able to get the results that I've got, show that cycling really has changed. If people are doping it's not working – they're not winning the races any more, that's for sure.

Froome also believes that the reaction of the peleton to the recent positive tests of French rider Sylvain Georges and the Italians Mauro Santambrogio and Danilo Di Luca showed that times have changed.

"I was quite happy to see the response," said Froome. "It is just not accepted any more. You are not going to have any friends in the bunch if you come back from a two-year doping ban in this day and age.

"I feel that the omerta has been broken. Anyone now who does [drugs] is not only costing them their career – it is potentially taking down a whole team of cyclists plus the 50-odd support men around them. It is clear that those guys were acting on their own. They are the minority, the absolute minority and it's great that the tests picked them up."

Meanwhile Froome believes that the huge upswell of British cycling fans in recent years will inspire him when the Tour finally begins.

"I definitely feel like I'm flying the flag for Britain this year, given the enormous energy and support we have had from last year's Tour through the Olympics and into this year, it really is mind-blowing," he said. "It's great to see how many people are behind us.

"There's the sense that we have got a whole nation behind us now. As opposed to before, when it felt like not too many people really cared what was happening in the Tour de France."