to the BBC, Pierre Bordry, the head of the French Anti-Doping Agency (Agence Française de Lutte contre le Dopage, AFLD) has raised concerns over the reliability of tests scheduled to be carried out by the sport's governing body, the International Cycling Union (UCI), during this year's Tour.
Last year the AFLD and the UCI shared responsibility for testing but, as the BBC reports, there was friction between the two bodies with the French claiming that the UCI had given some top riders preferential treatment and had relied only on screening samples rather than backing them up with customs information and police investigations.
The UCI will conduct tests alone this year with observers from the World Anti-Doping Agency, Wada, on hand to oversee the screening process.
As far as Bordry is concerned that's proof that Wada also has some doubts about the UCI's ability to keep the Tour drug-free.
"I think if this year there are three people from Wada to control UCI, surely there is a reason for that," he told the BBC.
Bordry is also critical of the new passport introduced by the UCI to establish a "biological profile" of every rider based on blood and urine samples taken throughout the year.
It's supposed to set a norm of levels for each rider but Bordry says cycilsts can easily "cheat the system" by taking small but regular amounts of doping substances.
Bordry is not alone in his concerns ahead of this year's Tour.
Bloomberg News reports
that while testing in cycling has become more rigorous, riders have found new ways of cheating.
"Cyclists are transfusing less blood and injecting smaller doses of stamina-building drugs to try to get around more intensive doping tests, according to four scientists who analyse exam results," it says in a report that looks at the general problem of doping in cycling.
“I’m afraid things are as bad as they’ve ever been,” Michael Ashenden, an anti-doping researcher on Australia’s Gold Coast told Bloomberg News.
"What I see is the incidence of riders trying to dope and avoid detection isn’t very different to how it has been throughout history.”
The UCI has defended both its passport and its testing, insisting that it does more than most other governing bodies to try to combat drug-taking.
"We have created the most sophisticated tool that many other international sports organisations would like to introduce," Enrico Carpani, a UCI spokesman told the BBC.
"We are explaining, we are selling the biological passport to other federations so that's proof that this new approach is the most important and the most reliable that sport has today to fight against doping."
This year's Tour de France
, the 97th edition of the race, will begin on Saturday with the prologue in the Dutch city of Rotterdam.
The final stage will be on July 25 with riders crossing the line on the Champs Élysées in Paris.