New York - Lance Armstrong is still telling lies over the extent of his doping despite his confession to Oprah Winfrey, according to the head of the World Anti-Doping Agency, John Fahey.
Fahey said Armstrong had lied in the interview when he said he stopped doping after 2005 when he won his seventh Tour de France.
Armstrong retired after the race before making a comeback in 2009 but said he raced clean in his return.
VIDEO: Armstrong on telling his son the truth
"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 London's Daily Telegraph on Friday.
"Believe USADA or believe Armstrong? I know who to believe."
Fahey suggested that Armstrong's stance might be in order to avoid further legal issues in America. He also accused Armstrong of giving 'weasel answers' in the interview with Oprah in a 'controlled PR exercise'.
“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.'
Armstrong evaded many of the questions asked by Winfrey and was heavily criticised for showing little contrition, but those who know him said that was typical of his character.
"He's never been one to be super apologetic," his former team-mate, Tyler Hamilton, told CNN on Friday.
"I don't ever think he apologised back in the day when we were team-mates for a whole lot of anything, really.
"He doesn't show a lot of emotion. Last night I did see - for Lance Armstrong - quite a bit of emotion ... by his standards."
Hamilton was one of the riders who helped bring down Armstrong, providing sworn evidence to the United States Anti-Doping Agency (USADA) that Armstrong used banned substances.
Hamilton also confessed to cheating and was subsequently stripped of the gold medal he won at the 2004 Athens Olympics.
He said he felt vindicated by Armstrong's admission.
"It's nice to hear him finally own up to some of his faults," he said.
Another British newspaper, the Sunday Times, said it would vigorously pursue a £1m legal action against Armstrong following his admission.
The Sunday Times paid Armstrong in 2006 to settle a legal case after it had questioned what was behind his Tour de France wins in an article published in 2004.
The newspaper, part of Rupert Murdoch's media business, also wants to recover interest and legal costs incurred in the case.
"We watched Lance Armstrong's interview with interest and noted his numerous admissions regarding taking performance-enhancing drugs," a Sunday Times spokesperson said.
"The Sunday Times believes that our case for recovering the £1m he obtained from us by fraud is now even stronger. We will be pursuing that case vigorously."
A lawyer for SCA Promotions, a Dallas-based insurance company, said it would take legal action against Armstrong unless he repaid them more than $12m they gave him for his Tour de France wins.
Tillotson said the company would make a decision on the lawsuit after watching Friday's second and final part of the interview.
"No one should underestimate the resolve of SCA," Jeff Tillotson told Reuters.
"If it doesn't get back its money, SCA will sue Mr Armstrong for the refund of that money, and it will be soon."
The International Olympic Committee (IOC), which announced on Thursday that it had stripped Armstrong of the bronze medal he won at the Sydney 2000 Games, said Armstrong had done nothing to redeem himself in the first part of the interview.
"If Lance Armstrong believes he can win credibility with this interview then it is too little, too late," IOC Vice-President Thomas Bach told Reuters.
"There are no new facts or evidence related to the USADA (US Anti-Doping Agency) report in the entire interview. It was clearly a well-orchestrated interview which, however, did provide no new facts."