Rusedski recently returned from a series of injuries

The 30-year-old confirmed he had failed a test for nandrolone and will face a hearing in Montreal on 9 February.

The British number two said: "I shall attend and I fully expect to be found innocent. I do not and have not taken performance-enhancing drugs.

"This is a very complex situation which once understood will clearly demonstrate my total innocence."

Speaking in Adelaide later on Friday, he reiterated his innocence before flying to Sydney, where he was whisked out of the airport via a side exit to avoid the waiting media.

Should he be found guilty, Rusedski faces a two-year ban from the sport and almost certainly the end of his career.

News of Rusedski's failed test stunned the tennis community.

The Lawn Tennis Association's national manager Mark Petchey said he found it hard to believe that Rusedski, whom he described as a "model professional", would knowingly use a banned substance.

If it does turn out to be true it will be hugely damaging to tennis LTA's Mark Petchey

"Knowing Greg for a long time he'd be the last guy that I would say would take performance-enhancing drugs," said Petchey.

"He's just such a model professional. He just would not have gone anywhere near this.

"If it does turn out to be true it will be hugely damaging to tennis - and British tennis in particular."

The LTA's performance director David Felgate added: "I am surprised he has gone public before the hearing.

More reaction: Cash rounds on Rusedski

"I had heard the rumours over the last couple of days but I am as staggered as anybody else.

"He prides himself on how he works out and tries to keep himself in shape and as far as I'm concerned is a thorough professional."

Rusedski's former coach Tony Pickard told BBC Radio Five Live: "I believe Greg is telling the truth when he says he is innocent but, unfortunately, he is responsible for what is in his body."

Rusedski's contemporaries on the ATP Tour were also surprised by the news that the Briton had tested positive.

"I've got to give him the benefit of the doubt because I know him and I would be pretty surprised if the guy has taken something," said Spanish veteran Alex Corretja.

American James Blake added: "I hope it is just a mistake and he's back on tour and he's okay. You have to be careful putting things in your body when your body is your profession."

Meanwhile, former Davis Cup player Barry Cowan is in no doubt that if Rusedski is found to have taken illegal drugs, then he should be banned.

"It's like any case, Greg will have to consult his lawyers," said Cowan.

Of all the people to have been found guilty of taking a performance-enhancing drug, Greg would have been bottom of my list Andrew Castle Former British number one

"He will appeal and it will be a long, drawn-out process - and hopefully it will be resolved in the right way.

"If he's proved innocent then fantastic, if he's proved guilty then he has to be banned."

And former British number one Andrew Castle admitted to being shocked by the news.

"Of all the people to have been found guilty of taking a performance-enhancing drug, Greg would have been bottom of my list," he said.