Many observers feel that Armstrong has still more questions to answer following his interview with Oprah Winfrey - with one former competitor branding the American a "disgusting human being."

Former Irish professional cyclist and anti-doping campaigner Paul Kimmage has described Lance Armstrong's admission as the start of a process.

Speaking on Morning Ireland,  Mr Kimmage said interviewer Oprah Winfrey failed to get to the bottom of some of the most critical issues, such as how Lance Armstrong had got away with doping.

"He says 'I never tested positive', well he did test positive and she didn't pull him on that, she should have said you did test positive, you tested positive in 1999, tell us how you got away with that, it is absolutely critically important that that is explained, "Kimmage said.

"I'm not interested in Lance Armstrong... he's not the problem, the problem is the sport, the important thing for me is the sport... and unless the lesson is learned from Lance Armstrong, this is going to happen again."

Kimmage said that he believed the only thing that Lance Armstrong was sorry about was that he got caught.

He added that the only service Armstrong could do for cycling was to testify under oath about his drug taking.

"I don't know whether he wants to leverage that (his admission of guilt) against something else, whether he's trying to cut a deal that would enable him to compete in triathlons and that, if he's genuine about it he'll be knocking on Travis Tygert's door today and saying ok I will testify under oath, I want to do this sport a service, I've caused it terrible damage.

"I know i can do it a service now, I can tell you exactly, what I did, how I did it and who enabled me to do it. That's the only service he can do the sport now."

David Walsh, The Sunday Times' chief sports writer, is widely credited with much of the investigative journalism which contributed to Armstrong's downfall.

Walsh wrote on Twitter: "First reaction is Oprah began the interview brilliantly with her series of 'yes or no' questions. It felt good to hear him admit to doping.

"Too many questions not answered and refusal to confirm hospital room admission was deeply disappointing. Betsy Andreu will be disgusted."

Betsy Andreu, the wife of Armstrong's former team-mate Frankie Andreu, claims she heard the 41-year-old telling doctors at Indiana University Hospital that he had used performance-enhancing drugs. He was being treated for cancer at the time.

Armstrong described Betsy Andreu as "crazy" and he told Winfrey he had apologised to her for that, but would not confirm the hospital conversation took place.

Emma O'Reilly, a former masseuse with US Postal who spoke out about Armstrong's misdemeanours, was another who felt his wrath.

Walsh went on: "I was pleased Oprah reminded him he had called Emma O'Reilly a whore. And pleased he confirmed Emma's account of cover-up of 1999 positive.

"Lest anyone forget, he did this interview because his reputation/brand was in the gutter. Only time will tell how much it helps.

"When he said he was behaving like a jerk during those years, I thought 'Lance, I could have told you that back then."'

Broadcaster Phil Liggett, who has worked closely with Armstrong for some time, believes there could be further revelations to come and that the 41-year-old could not have acted alone.

Liggett told Press Association Sport: "I still feel as though the show was a little bit soft on Lance.

"He hasn't really shown any real regret. He's not repenting.

"But he hasn't implicated anyone else and he could not have done this alone.

"Lance made it quite clear this was an interview about his confessions and not anybody else's."

World Anti-Doping Agency chief executive John Fahey insists chemical evidence shows Armstrong did dope during his comeback years - in 2009 and 2010 - despite the Texan's claims to the contrary.

"The evidence from USADA is that Armstrong's blood tests show variations in his blood that show with absolute certainty he was doping after 2005," Fahey told The Daily Telegraph.

"Believe USADA or believe Armstrong? I know who to believe.

"It struck me that the statute of limitations under US law might be relevant and Armstrong would not want to admit to anything in regards to his comeback (in 2009) that might be picked up under the US criminal code.

"This bloke is a cheat and did my view of him change after watching the interview? No."

Britain's former Olympic champion Nicole Cooke, who openly criticised drug cheats including Armstrong and Tyler Hamilton in her retirement statement earlier this week, was in no mood to back down after watching the interview.

After Armstrong claimed he only doped to create "a level playing field", Cooke told BBC Radio Five Live: "If he was trying to convince himself by arguments like that, he's got no morals - he is a disgusting human being.

"The sad thing is that there were clean riders who had livelihoods, whole careers stolen from them by that. We're probably not going to see those people vindicated in any way through this.

"I don't think he grasps the scale of what he's done and its impact on so many people."

Cooke insists there are still questions to answer about Armstrong's doping and the other parties involved.

"I think we still need to get to the bottom of the Lance Armstrong fraud," she said.

"He's got no morals - he is a disgusting human being" - Nicole Cooke pulls no punches in her assessment of Armstrong

"Floyd Landis (who was also stripped of a Tour title) said that he was able to cover up his positive tests with officials and we really need to find out the answer to those questions. We're close to the bottom but we still need to uncover the last few things."

Betsy Andreu was far from satisfied with Armstrong's confession.

"I'm really disappointed," she told CNN.

"He owed it to me; you owed it to me Lance, and you dropped the ball. After what you've done to me, what you've done to my family, and you couldn't own up to it.

"And now we're supposed to believe you? You had one chance at the truth; this is it. If he's not going to tell the truth, if he can't say 'Yes the hospital room (and confession to the doctor about drug use) happened,' then how are we to believe everything else he's saying?

"He won't do it because it did happen. That's not being transparent. That's not being completely honest.

"I want to believe that Lance wants to come clean, but this is giving me an indication that I can't.

"We're already questioning him."

Betsy Andreu dismissed many of the answers made by Armstrong, including the suggestion he was not the leader of the team. Her husband, Frankie, did not have his contract renewed, she alleges, after refusing to take part in a doping programme.

She added: "This is a guy who used to be my friend who decimated me. He could've come clean. He owed it to me. He owes it to the sport that he destroyed.

"When he says he doesn't like the UCI, that's a bunch of crap. He had the UCI in his back pocket.

"Lance wasn't a leader. That's a bunch of crap, because he owned the team.

"Why did they make sure Frankie's contract wasn't renewed in 2000?"