THE AUSTRALIAN Sports Anti-Doping Authority has refuted allegations of hypocrisy, declaring it has "no vendetta" against any AFL club or individual.

ASADA felt compelled to reinforce its stance that it operates "without fear or favour" after its decision to clear former Gold Coast player Nathan Bock of doping drew criticism.

The anti-doping body investigated Bock for allegedly injecting himself with the banned drug CJC-1295 in 2010, but found insufficient evidence to sustain a charge.

This development prompted the lawyer of disgraced former Essendon coach James Hird to tell News Corporation that ASADA had acted with "bare-faced hypocrisy", given he felt there was a similar lack of evidence in the case of the banned Essendon 34.

ASADA hit back in a detailed statement released on Saturday afternoon.

"ASADA pursues those cases where there is a strong body of evidence and those cases where ASADA believes they can be proven to comfortable satisfaction," the statements read.

"Allegations against AFL players are heard in the first instance by the AFL Tribunal.

"We note that the Tribunal was not comfortably satisfied that Mr Dank had trafficked CJC-1295 to the Gold Coast in 2010. The Tribunal was comfortably satisfied that Mr Dank had attempted to traffick CJC-1295, however the Tribunal was not comfortably satisfied that the substance believed to be CJC-1295 was in fact the prohibited substance CJC-1295.

"ASADA chose not to appeal those findings.

"Allegations need to be corroborated with other evidence to be proven. In the matter of the Gold Coast Suns, despite thorough investigations, ASADA considered there was insufficient supporting evidence.

"In comparison, other cases pursued as a result of Operation Cobia have been supported by an accumulation of convincing evidence including scientific analyses, corroborating statements from multiple parties and text messages discussing prohibited substances.

"ASADA has no vendetta against any club or person, and history has shown we are not afraid of taking on the tough cases. But to take on the hard cases we require sufficient evidence.

"ASADA investigated a number of players and clubs as part of Operation Cobia, but that does not mean that there was reliable, or substantial, evidence of violations in all these matters.

"ASADA is committed to clean sport and will continue to pursue those cases where there is sufficient evidence, without fear or favour."