The corruption watchdog has been accused by the WA Police Union of intimidating, bullying and threatening officers.
Union president George Tilbury told a parliamentary committee this morning that officers had been brought to tears and forced to take stress leave because of the tactics used by Corruption and Crime Commission investigators.
Mr Tilbury said the approach of the CCC was "akin to a vendetta" against police and no other public agency or department was subjected to the same level of scrutiny.
"The lack of respect shown to our members by the CCC is a disgrace," Mr Tilbury told the committee which oversees the corruption watchdog.
Mr Tilbury was giving evidence at an inquiry prompted by the union advising officers in July not to take part in voluntary interviews with the CCC.
He said officers had no legal protection when taking part in voluntary interviews, which lasted up to three hours.
Mr Tilbury dismissed concerns that there was a "Mexican stand-off" between police and the CCC, saying he was unaware of CCC Commissioner Roger Macknay's reason for referring the matter to he committee.
Mr Macknay has previously told the committee that the decision not to give voluntary interviews threatened to thwart the CCC doing its job.
But Mr Tilbury said the issue had been completely blown out of proportion and involving the committee was a waste of time.
He said the advice to police officers had been given in the context of an escalation of CCC investigations into police and the complaints about its tactics of bullying and intimidation.
He said he had one email outlining details of the complaints, but other issues had only been raised verbally because officers we're fearful of reprisals.
He also raised questions about the impartiality of CCC Parliamentary Inspector Michael Murray, telling the committee that the inspector had formed a view on the issue of voluntary hearings and written to the CCC without hearing the views of police.
Committee chairman Nick Goiran said he was not satisfied that the concerns about impartiality, directed at a person of Mr Murray's eminence and experience, were sustainable on grounds provided and suggested the union should make detailed submissions to the committee if it wanted to pursue the matter.