Exclusive: Floyd Landis on Lance Armstrong

July 23, 2010 - -- On a warm summer's night this week in Bend, Ore., the man at the center of one of the biggest scandals in sports history couldn't have looked more out of place.

Floyd Landis was racing his bike in a simple T-shirt -- no fancy cycling jersey.

It has been an epic fall from grace for Floyd Landis.

But the former Tour de France winner's biggest surprise wasn't the disgrace of losing his Tour title -- or of being banned from the sport he loves as a drug cheat. It was the decision to come clean about his own doping and make sweeping accusations against others, including one of the biggest names in all of sport, Lance Armstrong.

CLICK HERE to watch the full report on Floyd Landis, Lance Armstrong and performance-enhancing drugs in cycling

"If I'm taking on Lance Armstrong, then that should be evidence enough that there's a problem with the system, because I'm saying it -- a bunch of people did it," Landis said. "Look. At some point, people have to tell their kids that Santa Claus isn't real. I hate to be the guy to do it, but it's just not real."

We asked Landis: You're saying Lance Armstrong is a fraud?

"Well, it depends on what your definition of fraud is," Landis said. "I mean it -- look -- if he didn't win the Tour, someone else that was doped would have won the Tour. In every single one of those Tours."

An attorney for Armstrong, Tim Herman, adamantly denied Landis' allegations against Armstrong. He went on to say that Armstrong has undergone around 300 separate competition drug tests and never tested positive.

"I know [Armstrong] to be an athlete that comes along once every couple of generations," Herman said. "He is extremely focused. He's gifted physically in ways that are very unique and he is disciplined, dedicated. He's the hardest working athlete I've ever been around. But he's also extremely devoted and committed to his cancer work. ...

"Landis is a confessed perjurer and he is a liar, and I think, as Lance said ... when you taste milk to see if it's sour, you take a first taste and you don't have to drink the whole carton to know it's all sour."

Floyd Landis on Lance Armstrong

In the sporting world, the Landis allegations, printed but never before broadcast, have been a bombshell of unprecedented proportions.

And that is because Armstrong is a superstar of unprecedented proportion.

Armstrong is so famous he's practically branded the color yellow as his own: that yellow jersey and those ubiquitous yellow bracelets evoke his image as a golden boy, an American hero who beat cancer and the competition, who brought in millions and who manages to keep movie stars and world leaders alike on speed dial.

But Landis, Armstrong's former teammate, painted a much less glamorous picture of cycling's greatest.

Over the course of a 90-minute interview, Landis described in detail for "Nightline" how he says he and fellow cyclists -- his former friends -- doped during the Tour de France.

In the past, Landis has denied using performance-enhancing drugs. So why would anyone believe him now?

It's a question U.S. federal investigators are taking seriously. The same federal agents who took on steroid use in baseball are now probing Landis' claims in a very big way, issuing subpoenas to riders and team sponsors and reportedly going after Armstrong and his former U.S. Postal Service cycling team.

Authorities have not contacted Armstrong, Herman said.