Champion swimmer Dawn Fraser says she has known for years that top Australian athletes have been taking drugs, a fact that "sickens" her.

Her comments came as Australian Olympic Committee (AOC) president John Coates admitted the doping scandal enveloping track cycling and now weightlifting had tarnished Australia's clean reputation.

Speaking to Sky News, Fraser said she had known about top athletes using drugs for years.

"I'd hate to think we get some athletes over there (the Athens Olympics) that win medals and prove positive on their drug tests and I can see that happening," Fraser said.

"I've known about it for quite a number of years and I know that some of our top-line athletes have been taking these drugs."

"It sickens me to think they needed these drugs to help them gain to the best of their ability," she said.

"They know who they are and they have got to sleep at night, I just hope they wake up to themselves."

Weightlifter Caroline Pileggi was on Friday thrown out of the Athens team after refusing a drugs test, and former world champion track cyclist Jobie Dajka has had his place put on hold pending two investigations.

Dajka is one of five cyclists to be investigated by retired WA judge Robert Anderson in recent weeks.

"I think mud does stick, there's no doubt about that," Mr Coates told reporters in Sydney.

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