World Anti-Doping Agency president John Fahey on Friday branded Lance Armstrong's doping confession a "controlled public relations" stunt that revealed nothing new.

As influential South Australian Senator Nick Xenophon threatened legal action to force the state government to reveal how much it paid Armstrong to ride in the Tour Down Under, Fahey attacked both Armstrong and world cycling body UCI.

Fahey told the Fox News Australia television station that all the 41-year-old Armstrong did in his interview with Oprah Winfrey was confirm details of his doping that were already public knowledge.

"There's nothing new from my point of view," Fahey said. "All he did was affirm what the US Anti-Doping Agency had put out in a very substantial and irrefutable judgement some months ago -- that this man had taken all sorts of substances for performance purposes.

"He denied that until this point, but there was little doubt he was doing that, and all he did was confirm that today in a very controlled manner."

Fahey was especially damning of Armstrong's choice of forum to confess, saying he should have appeared under oath at an "appropriate tribunal" where he could be cross examined.

"Where he would have to name names, tell of the officials, the entourage, who supplied the drugs, when, where, and which riders were associated," Fahey said.

He reiterated that WADA would not take part in the UCI's independent commission into Armstrong's doping as it believed the terms of reference were not broad enough.

"They are focused on, it seems, trying to absolve any role UCI might have had with Armstrong," he said. "They've never come to us to discuss the terms of reference or to get any advice from us at all.

"I don't think they're sincere about trying to clean up their sport when they're going down this particular path, which I believe will lead them nowhere."

Xenophon, who sits as an independent in the Australian Senate, said the South Australian Government should now make public just how much it paid the American to ride in the Tour Down Under for three years from 2009-11.

The fees are believed to amount to several million dollars, but South Australian Premier Jay Weatherill has refused to disclose the exact amount.

"A court should have regard to Armstrong's confession and how that would work against the commercial-in-confidence argument," Xenophon said.

"Releasing details of the taxpayer funds paid to Armstrong couldn't possibly undermine the event in any way."

Earlier this week Weatherill said the government would not reveal how much Armstrong was paid because it would indicate to others how much it was prepared to spend to support major events.

He said the government was protecting its own interests, not Armstrong's, by keeping the figure secret.

Armstrong used the event, which begins in Adelaide on Monday, to launch his comeback to professional cycling in 2009.

On Thursday's Oprah show, the disgraced cycling legend admitted that his seven Tour de France titles were fuelled by an array of drugs.

"And I'm sitting here today to acknowledge that and to say I'm sorry for that," said Armstrong, who kept any emotions in check as he described years of cheating, lying, and attacking those who had the temerity to doubt him.

"I view this situation as one big lie that I repeated a lot of times," he said.