In this file photo taken on August 18, 2008, Australia's goalkeeper James Stanton watches for a shot by a Montenegro player in a preliminary round men's water polo match at the 2008 Olympic Games in Beijing. [Photo/Agencies]

SYDNEY - Australian James Stanton's dream of playing water polo at a third Olympics has been dashed by a two-year ban after he tested positive for a banned anabolic agent on Wednesday.

The 27-year-old goalkeeper, who denies wittingly using a banned substance, tested positive for clenbuterol in an out-of-competition test in Perth last year.

Stanton's ban has been backdated but he will still be unable to compete until October next year and so will miss out on the London Games, which take place from July 27 to Aug 12.

"I wish to make it clear that I have never knowingly taken any performance-enhancing substance and to do so would go against everything I believe in as a person and a competitor, and everything I have stood for in my career," Stanton said in a statement.

The World Anti-Doping Agency (WADA) reiterated in a statement last week that any level clenbuterol in a sample remained banned.

Spain's Tour de France champion Alberto Contador tested positive for the agent last year but said he had inadvertently consumed the substance in contaminated meat.