The International Cycling Union's independent commission into drug use in the sport was thrown into disarray after it lost the support of both the world and American anti-doping authorities.

World Anti-Doping Agency president John Fahey released a statement to say his organisation would take no part in the commission because of a number of issues - one of which was a concern that it was too strongly focused on Lance Armstrong.

WADA is also unhappy the commission will offer no immunity to cyclists willing to come forward and give evidence, a concern echoed by the United States Anti-Doping Agency and its chief executive Travis Tygart.

Relations between the UCI and USADA have been strained for some time, but it is the withdrawal of WADA from the commission which threatens to damage to credibility of the exercise.

Fahey highlighted the issues which worried his organisation, saying: "WADA has shared a number of serious concerns as to the commission's terms of reference and its ability to carry out its role without undue influence.

"In particular, WADA is concerned that the scope of the inquiry is too focused on sanctioned former cyclist Lance Armstrong - especially as his case is closed and completed with there being no appeal - and will therefore not fully address such a widespread and ingrained problem.

"WADA also has concerns over the timeframe agreed for the Commission. A June deadline for the commission's report is wholly insufficient and will result in a lost opportunity to properly investigate the problem.

"There is further concern that the UCI has had too much influence over the terms of reference, which calls into question the Commission's independence. The terms of reference were signed off by the UCI and the Commission without consultation with anti-doping authorities, while the requirement for the Commission to deliver its report to the UCI before any other party is unacceptable.

"Finally, because the Commission does not offer immunity there is no incentive for witnesses to come forward, or to even give witness statements. An approach that does not allow individuals to give evidence without the fear of retaliation will merely perpetuate the 'omerta' that has been an obstacle to cycling investigations in the past.

"Despite these concerns, WADA has been informed that the commission and UCI are not willing to change the terms of reference and timetable, and for this reason WADA has declined to spend money and dedicate resources on an inquiry that has such obvious limitations."

"The current terms of reference are not good for clean athletes or moving this sport forward to a better future" - Travis Tygart

The blow to the UCI comes with Armstrong very much in the headlines.

The 41-year-old's much-publicised interview with Oprah Winfrey, who revealed yesterday he had admitted to doping, is to be broadcast this week, with speculation yet more names could come to light to damage the sport's reputation further.

USADA, whose investigation into Armstrong put him at the head of "the most sophisticated, professionalised and successful doping programme that sport has ever seen" and precipitated the removal of his seven Tour de France titles, is also unhappy with the UCI's independent commission.

CEO Tygart said: "UCI's refusal to agree to allow a limited opportunity for riders to come forward and be truthful without fear of retribution or retaliation from the UCI obviously calls into question the UCI's commitment to a full and thorough investigation and creates grave concern that the UCI has blindfolded and handcuffed this Independent Commission to ensure a pre-determined outcome.

"The current terms of reference are not good for clean athletes or moving this sport forward to a better future."

The UCI set up the commission in the wake of USADA's investigation into Armstrong which shone a light on a decade of drug use in the sport.

The commission is made up of British Paralympic great Tanni Grey-Thompson, former Court of Appeal judge Sir Philip Otton and Australian lawyer Malcolm Holmes and is due to meet throughout April.