Belgian rider Tim Wellens described the use of anti-asthma inhalers as tantamount to cheating, after four-times Tour de France champion Chris Froome failed a test for Salbutamol during last year's Tour of Spain.
Briton Froome, who suffers from asthma and denies breaking any rules, could potentially be stripped of his Vuelta a Espana title after results showed a urine test he gave during the race in September showed excessive levels of the asthma medication.
"To me, it's cheating. Sometimes, when you are sick, you don`t have a choice and you have to take it . But you can also choose to pull out (of the race)," Belgian TV station RTBF quoted Wellens as saying.
Wellens pulled out of the Tour de France last year because of breathing problems.
"I underwent tests at the hospital and I learnt that with an inhaler, I could increase my breathing capacity by 7 or 8 per cent. But I am against inhalers, I don't want to increase my breathing capacity in that way," the Lotto Soudal rider said.
"I would want things to be black or white, not grey."
Froome, who rides for Team Sky, says he has done nothing wrong and would provide whatever information world cycling's governing UCI requires.
Salbutamol is permitted as a legal asthma drug by the World Anti-Doping Agency (WADA), and the UCI said Froome's failed urine test did not necessitate a mandatory provisional suspension.
But riders have been banned for excessive use of it in the past, notably Italian Alessandro Petacchi who was given a 12-month suspension and stripped of his five stage victories in the 2007 Giro d'Italia.