Acting NSW Ombudsman John McMillan has declared he would not want the office to ever again conduct an investigation like the inquiry into the police bugging scandal, given the potential for reputational damage.
Professor McMillan said that while it was "understandable" that the government referred the inquiry in 2012, in hindsight a special commission of inquiry "may have avoided some of the controversies".
"The legal profession is far less likely to publicly attack a commission headed by somebody from the profession than somebody like an ombudsman," he told Fairfax Media.
"I had an office of 220 people to run. Necessarily … you're actively defending the reputation of the office.
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"A special commission of inquiry avoids those difficulties. I would not want the Ombudsman's office to have a task like this again."
In December, Professor McMillan published the report on the Ombudsman's four-year, $10 million Operation Prospect inquiry into a bugging operation carried out 17 years ago by NSW police, the Crime Commission and the Police Integrity Commission.
Deputy police commissioner Catherine Burn had a senior role in the operation that targeted corrupt officers but also innocent civilians and police, including former deputy commissioner Nick Kaldas.
Ms Burn and Mr Kaldas have applied for the job of NSW police commissioner after Andrew Scipione retires on April 2.
However, the Prospect report found Ms Burn engaged in "unreasonable" and "unlawful" conduct and Mr Kaldas faces possible criminal charges for allegedly giving "false and misleading testimony".
Mr Kaldas described the inquiry as "a debacle and massive miscarriage of justice" that tramples on his rights as a whistleblower. Ms Burn said while she made mistakes she acted "ethically, honestly" and in accordance with the law.
Asked if he had any reservations about Ms Burn and Mr Kaldas becoming police commissioner, Professor McMillan said: "I am aware they are both candidates. I've made adverse findings against them ... that's an issue for the selection panel to take up if it chooses."
Adverse findings were also made against the NSW Crime Commission, which on Monday responded by publicly criticising the Prospect report as "fundamentally defective" and carrying "limited weight".
But Professor McMillan rejected the response – which ranged from allegations he had insufficient qualifications to claims the Ombudsman was biased against the commission in favour of police – as containing "unfounded and inflammatory claims".
Professor McMillan, a former Commonwealth Ombudsman and Australian Information Commissioner, said he had 45 years' experience and "all of the qualifications".
"I have never experienced this level of antagonism to an Ombudsman investigation before," he said.
"I do have a deep concern that an office with a 40-year track record of independence and balance has come under unfounded attacks for doing a job that nobody else could do."