Marcel Kittel and André Greipel criticise Team Sky's TUE policy

We've not been short of critics for Team Sky's use of Therapeutic Use Exemptions to allow riders to take otherwise banned substances to treat medical conditions, but the words of Marcel Kittel and André Greipel could be the most scathing yet.

The British team has been under fire in recent weeks after hackers leaked details of TUEs approved for the likes of Sir Bradley Wiggins and Chris Froome, both of who suffer from asthma.

While there is no suggestion of wrongdoing on the part of the team or the riders, Kittel and Greipel made their thoughts on the matter very clear ahead of the World Championships road race on Sunday.

"If you have trouble with your illness, then you should not ride a bike [professionally]. We at Lotto-Soudal are in the MPCC (Movement for Credible Cycling). Now you know why Sky is not there," Greipel said.

Kittel was slightly more blunt with his assessment, with the German Press Agency article claiming he said that riders who suffer from asthma severe enough to require a TUE should compete at the Paralympic Games.

The rider, however, clarified his comments on Friday afternoon, saying his remarks had been taken out of context.

Fellow German sprinter, John Degenkolb, believes that an independent body should be set up to approve or deny TUEs to ensure fairness. All three riders have reportedly not made use of TUEs during their career.