Lance Armstrong has again issued a firm denial against the doping allegations which have cast a shadow over his cycling career.

The seven-times Tour de France champion, who is preparing to make a comeback in 2009, has been repeatedly accused of taking performance-enhancing drugs, with the claims continuing even after his retirement three years ago.

Armstrong's return has provoked controversy, with some critics insisting samples the American provided during his record run of titles from 1999 to 2005 should be tested again.

But the 37-year-old, who beat testicular cancer to become the leading Tour rider of all time, is adamant he is innocent of all doping allegations and his success is due to hard work.

"There has been a fair amount of suspicion around me," Armstrong said.

"The level of scrutiny I've had throughout my career from the press and the anti-doping authorities is unmatched.

"I've got nothing to hide. There are seven cups in this room because of my hard work. Next year won't be any different, even if people hate to hear that. There are no secrets."

Armstrong (above), who is due to return in the Tour Down Under in Australia in January, will fight against having his old samples re-tested. "Nobody in their right mind would take that test," he said.

"Something might have been put in it and your life, your credibility, depends on it. I'm all for drug controls but if the athlete cannot defend himself, what kind of kangaroo court is that?"

Meanwhile, Italian Riccardo Ricco has appealed his two-year doping ban to the Court of Arbitration for Sport.

Ricco was banned by the Italian Olympic Committee last month for doping during this year's Tour de France in which he won two stages.