Andy Murray has been a strong proponent of stricter anti-doping regulations.

The world No. 2 is calling for more transparency over the Therapeutic Use Exemptions some players have received.

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A Therapeutic Use Exemption permits a player to use a prohibited medication without committing an anti-doping rule violation, provided the player has a medical condition warranting use of the drug and that all use is in accordance with the conditions of the TUE.

In an interview with The Telegraph's Simon Briggs, Murray said: "I have never used a TUE in my life.”

The two-time Olympic gold medalist says some TUEs are valid, but others "are abused."

"I’ve seen quite a lot of it. I don’t think every TUE is bad, but there are TUEs that are abused, for sure," Murray said. "And I do think that now is the time when all TUEs should be transparent.

“Everyone should know, if an athlete is given a TUE, what it is they’re taking and the reasons for it. And also the medical reasons behind it because we don’t always find that out. Maybe that isn’t perfect and a lot of people like to keep their medical records confidential. But when things like this happen, it could clear a lot of things up.”

Last month, the Russian cyber hacker group Fancy Bears posted drug records revealing TUEs for Rafael Nadal, Venus Williams, Serena Williams, Bethanie Mattek-Sands and Laura Siegemund. All of those players held valid TUEs in past seasons.

After Maria Sharapova scored a partial appeal victory that reduced her initial two-year suspension for the banned drug meldonium to 15 months, Head CEO Johan Eliasch, questioned both the legitimacy of Sharapova's initial suspension and Therapeutic Use Exemptions granted to some tennis players.

"This calls into questions the revelations about certain Olympic athletes who were granted therapeutic use exemptions for substances that could most certainly be considered performance enhancing and have proven to be performance enhancing under significant clinical testing, while meldonium, the substance that Maria had been taking, has yet to be proven under any significant clinical testing to have any performance enhancing benefits," Eliasch said in a statement. 

Murray, who like Sharapova is a long-time Head endorser, was one of several players who took a strong stand saying Sharapova should be banned after her positive test.

“It’s not up to me to decide the punishment, but if you’re taking performance enhancing drugs and you fail a drug test, you have to get suspended," Murray said at Indian Wells in March.