Australian drug experts have challenged claims by Australian Open tennis champion Petr Korda that he was unaware he had used a banned steroid.

But organisers of next month's Australian Open at Melbourne confirmed in Sydney yesterday that there would be no question of Korda not defending his title.

Tests administered during the last Wimbledon championships revealed the presence of the steroid nandrolone, but Korda said he had no idea how the substance had been administered to him.

The Czech world number 10 was forced by the International Tennis Federation to forfeit the $94,529 he won as a Wimbledon quarterfinalist.

But the ITF declined to suspend the 30-year-old because it was satisfied he was unaware he had taken the banned substance.

Australian Sports Drug Agency spokeswoman Vicki Kapernick said nandrolone was an artificial version of the hormone testosterone which could only be injected.

Sports medicine practitioner Dr Peter Larkins said: "It just doesn't gel with me, that he didn't know what it was, especially at that elite level."

However, Korda said in a statement: "I wish to state categorically that I am not a drugs cheat."