Chris Froome says questions remain over Team Sky and Bradley Wiggins seeking permission to use triamcinolone.

Wiggins in 2012 became the first British Tour de France winner and Froome has since inherited the Team Sky leadership and won the maillot jaune three times, in 2013, 2015 and 2016.

Data stolen by hackers from files held by the World Anti-Doping Agency showed Wiggins received three therapeutic use exemptions (TUEs) for anti-inflammatory drug triamcinolone — a substance which has a history of abuse in cycling and is otherwise banned — on the eve of the 2011 and 2012 Tours and 2013 Giro d’Italia.

Wiggins and Team Sky principal Dave Brailsford, the British Cycling performance director until April 2014, have strenuously denied any wrongdoing, insisting each time the TUEs were medically necessary to deal with a pollen allergy that aggravates Wiggins' long-standing asthma condition.

The TUEs also had the approval of the UCI, cycling’s world governing body, and there is no suggestion that Wiggins, who left Team Sky in April 2015, or the team, have broken any rules.

Froome’s two TUEs were published on the same day by hackers Fancy Bears, although already well known.

But Froome was unaware of his former team-mate’s TUEs.

“I was surprised, it was the first that I had heard of them,” he told cyclingnews.com.

“I had seen Bradley Wiggins using his inhalers so I knew he had asthma, but I wasn’t aware of his allergies.

“Without knowing the exact details of his medical condition, it’s impossible to say if he was operating in a grey area.”

Froome’s two TUEs were for short courses of prednisolone, a steroid used to treat acute chest complaints, in 2013 and 2014.

The latter was controversial at the time as it was granted to enable the 31-year-old Froome to take part in a key Tour de France warm-up race in Switzerland, despite being ill a week before.

His TUE application was cleared by cycling’s world governing body the UCI and WADA and he went on to win the Tour de Romandie.

Cyclingnews.com said it asked Froome the difference between the TUE cases, with the 31-year-old replying by email, outlining the history of the case.

“This is the standard treatment for post-infection inflammation in asthmatics that cannot be controlled by standard inhalers,” Froome added.

“I don’t believe that there are any alternative treatments, and performance enhancement is negligible.

“With regards to Wiggins’ TUEs, questions remain over his symptoms, the choice of treatment and the related performance benefits from that treatment.”

Froome also called for “stricter rules” governing TUEs.

UCI president Brian Cookson, who was British Cycling president until his election to the world governing body in September 2013 and also sat on the Team Sky board, says Team Sky and Wiggins operated within the rules.

“The issue of the substances issued to Wiggins appears to have been within the rules,” Cookson told reporters at the UCI Road World Championships, which concluded in Doha on Sunday.

“But I think there is an argument to be had about whether TUEs for that kind of substance are valid.”

Since the TUEs leak, UK Anti-Doping has launched an investigation into allegations of “wrongdoing” in cycling.

The Daily Mail reported Team Sky and Wiggins were under scrutiny over a package delivered to Brailsford’s squad at the June 2011 Criterium du Dauphine race in France.

Brailsford says he provided a “running commentary” of his personal fact-finding mission, which contained errors to make the situation “a damn sight worse than it needed to be”.

Brailsford has determined what was in the package. But the Team Sky principal is not prepared to reveal the package’s contents and prefers that the UKAD investigation can take place, so his team can be exonerated by an independent third party.

Team Sky, launched with a zero-tolerance policy to doping in 2010, “strongly refute” allegations of wrongdoing and are co-operating with the UKAD investigation which Wiggins has also welcomed. British Cycling is also co-operating.

Froome, who has been on a family holiday in recent weeks, added: “It’s a great shame for the sport that we’re once again debating the validity of a Tour de France victory, and it has been a very challenging time for those involved.

“Like many other members of the team, I look forward to the conclusion of the investigation that is currently taking place and getting back to focusing on the season ahead.”

Despite hinting at a difference of opinion with Brailsford, Froome offered his support to the Team Sky boss.

“Mistakes have been made along the way, but Dave B has created something incredibly special,” Froome added.

“I’m grateful to be in the position that I am, surrounded by an amazing team on and off the bike, with the best support structure in the pro peloton.”