Governing body, the UCI, wrote to the Spanish government to ask them to overturn a decision to stop evidence being used for disciplinary action.

UCI president Pat McQuaid said: "I urge you to intervene because of the damage this is causing to our sport.

"This is a ridiculous, serious and exasperating situation for the UCI and I am writing to you to help us."

McQuaid's letter to Spain's sports minister Jaime Lissavetzky was leaked to the Spanish newspaper El Mundo Deportivo.

The UCI verified the leaked statement rang true to McQuaid's letter, which went on: "Although I am aware that you are only interested in the criminal aspects of this case, I urge you to intervene.

We feel like spectators in this matter which is frustrating UCI spokesman Enrico Carpani

"If this lack of information continues in 2007 it will do irreparable damage."

Operation Puerto was launched after police raids on addresses in Madrid and Zaragoza in May found large quantities of anabolic steroids, laboratory equipment used for blood transfusions and more than 100 bags of frozen blood.

However, as doping is not an offence in Spain, the investigation is centred on criminal charges against public health, and the judge has ruled the evidence cannot be used to instigate disciplinary action against the cyclists.

That ruling meant charges against former Tour de France winner Jan Ullrich and 2005 runner-up Ivan Basso were dropped.

UCI spokesman Enrico Carpani said the whole affair was frustrating cycling chiefs, who are trying to clean up the sport.