SYDNEY — Chinese swimmer Sun Yang is a "drug cheat" who should not be competing at the world championships and governing body FINA need to "get off their backsides" to protect clean athletes, Australian swimming great Dawn Fraser has said.

Triple Olympic champion Sun was cleared to swim at Gwangju despite the Court of Arbitration for Sport (CAS) set to hear a doping case against him in September.

He has already claimed two freestyle titles at the worlds but his presence has angered rivals, with Australia's Mack Horton refusing to share a podium with him at the 400 meters medals ceremony and Briton Duncan Scott declining to shake his hand after the 200.

Fraser, who won the 100m freestyle at three different Olympics from 1956-64, told reporters in Sydney that FINA should never have allowed Sun to compete at Gwangju.

"I personally don't think he should be swimming," she said on Wednesday. "He's got a Court of Arbitration in September and I feel that FINA should have stepped him down until that court case is over.

"If he's proven not guilty, well that's fine, he can go back to swimming.

"I mean we go back to East Germany when all those German swimmers were caught with drugs. We want a clean sport and let's protest against it. FINA got to get off their backsides and do something about it."

Sun served a three-month ban for a doping offence in 2014 that was kept under wraps by FINA and the Chinese Swimming Association and emerged only well after it had expired.

Sun blamed the failed drug test that led to that ban on medication he said he was taking for a heart condition and did not know was prohibited.

His latest doping brush involves an aborted test last year in which he was alleged to have smashed a container holding one of his blood samples with a hammer.

He was cleared by a FINA Doping Panel in January over the test but the World Anti-Doping Agency (WADA) has filed an appeal to CAS.

Olympic champion Horton, runnerup in the 400 at Gwangju, labelled Sun a "drug cheat" at the 2016 Rio Games, triggering a fierce response in China.

His podium protest on Sunday was pilloried by Chinese state media and prompted a warning from FINA.

Fraser defended Horton for making his stand.

"Mack didn't say anything. He hasn't made any comment, he just didn't get on the podium to be with a drug cheat, and I support that," she said, calling for WADA and FINA to "do their job".

"At the moment, both of those (bodies) are fighting one another and WADA said he shouldn't be swimming.

"They should have the right to stop anyone taking drugs from swimming or competing in any sort of sport.

"We've been fighting for a clean sport for quite a number of years, its still hasn't taken place. There's still drug cheats out there and we want them banished." — Reuters