Chris Froome has revealed that turned down the use of a therapeutic use exemption during the second of his three Tour de France wins.
The Team Sky rider, who has admitted to receiving TUEs twice during his career, rejected medical help during the last week of his 2015 success.
The 31-year-old clung on to win a second yellow jersey by one minute and 12 seconds from Colombian rival Nairo Quintana, who finished the stronger of the two on the climb of Alpe d'Huez in the penultimate stage.
Froome has revealed he was struggling with an unspecified ailment but did not accept any assistance.
"I didn't feel having a TUE in the last week of the Tour was something I was prepared to do," he told the BBC.
"It did not sit well morally with me."
Cycling's use of TUEs - where banned drugs are allowed to be used to treat medical conditions - came under scrutiny after Russian hackers Fancy Bears published confidential details of athletes' TUEs.
Froome's two TUEs were both for a week's oral course of the anti-inflammatory drug prednisolone to treat chest infections that aggravated his asthma in 2013 and 2014.
Former Team Sky team-mate Bradley Wiggins - who also suffers from asthma and in 2012 became Britain's first Tour de France winner - was found to have had three TUEs for anti-inflammatory drug triamcinolone, taken on the eve of the 2011 and 2012 Tours de France and 2013 Giro d'Italia.
There was no suggestion that either Froome, Wiggins or Team Sky had broken any rules.
Froome has in the past spoken about his belief the TUE system in cycling is "open to abuse".
And he reiterated his desire for the World Anti-Doping Agency to clamp down on their use.
"The fact that we're having that debate about authenticity means there's a problem with the system," he said.
"I think Wada need to tighten their regulations around TUEs, so they're not something that we question, their legitimacy.
"It's not good for sport in general. The fact that we're discussing the validity of results, that brings it back to the authorities, it is something they need to tighten up on so that there aren't questions being asked anymore."
Meanwhile, an investigation remains ongoing into a jiffy bag delivered to Team Sky at the Criterium du Dauphine in 2011.
The UK Anti-Doping Agency is looking into the contents of the bag, which Team Sky principal Dave Brailsford last month told MPs was the decongestant Fluimucil.
The Guardian reported that Froome was asked whether Brailsford's ability to defend his own riders against allegations of doping had been damaged as a result of the saga and that he replied: "That's not for me to say. You'd have to ask (him) that."
He added: "Dave himself has put his hand up and said he has made mistakes. I think if you look at what Dave has actually done, the team he has put together, I think we've got a great group of guys with values in the right place."
