American Landis said in a statement posted on his website that USADA had stopped a rider's observer from attending the retesting of the samples at a French laboratory.
"This is yet another in a series of malicious actions by USADA that tramples my right to have my case heard in a fair and just way", said the 31-year-old Landis.
"How can I be expected to prove my innocence while USADA endeavors to break their own rules at every turn? I'm infuriated by the behavior of USADA and the (French anti-doping lab) LNNDD", he added. "Together, they have turned this proceeding into a full-scale attack on my civil rights and a mockery of justice."
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Seven samples taken during the 2006 Tour which had at first been tested negative were retested by the French lab, L'Equipe said.
The lab used a technique aimed at detecting exogenous testosterone as opposed to the male sex hormone naturally contained in the body.
The tests were conducted by the anti-doping lab in Chatenay-Malabry, outside Paris, and Landis's representatives as well as experts from the U.S. Anti-Doping Agency attended the procedure, L'Equipe reported.
The statement posted on Landis's website said, however, that a consultant to the rider, Paul Scott, had been denied entry to the lab on Sunday under the order of USADA.
Landis faces a disciplinary hearing in the U.S. next month after testing positive for testosterone during the 2006 Tour.
If found guilty of doping, Landis, who denies any wrongdoing, faces a two-year suspension from the sport and the possibility of becoming the first Tour winner to be stripped of his title.
However, the American could take the matter to the Court of Arbitration for Sport.
The French Anti-Doping Agency agreed in February to postpone its investigation into the case in exchange for a pledge by Landis not to race in the country in 2007, which means he will not take part in this year's Tour.
Landis is due to have a separate USADA hearing on May 14.
His lawyers say the samples were mislabelled by the French laboratory which conducted the initial tests that turned positive, the testing process was unreliable and the rider never in fact tested positive.
Testosterone can speed up recovery after exercise and generally improves stamina and strength.
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