An investigation into Walter Sofronoff KC as chair of a board of inquiry into the ACT's criminal justice system found he had engaged in the corrupt conduct.
"Mr Sofronoff's corrupt conduct has significantly undermined the integrity of the board's processes and the fairness and probity of its proceedings," the report from the ACT Integrity Commission concluded.
Mr Sofronoff's report of the inquiry delivered damning findings of unethical conduct against the territory's top prosecutor Shane Drumgold, who resigned.
But Mr Sofronoff leaked the report to journalists before its public release by the territory's chief minister, triggering a separate inquiry.
Mr Sofronoff claimed he had acted in the public interest to ensure media were informed about the issues investigated by the inquiry but the commission found he had not acted in good faith.
His conduct undermined the inquiry and threatened public confidence in its integrity.
"It therefore constituted serious corrupt conduct," the commission found in its report delivered to the territory's parliament on Tuesday.
No adverse findings were made against the journalists - The Australian's Janet Albrechtsen and ABC's Elizabeth Byrne - who received the report before its public release.
The inquiry found Mr Sofronoff's release of the report to Ms Albrechtsen was part of a pattern of conduct featuring "a very large number of communications with her throughout the course of the inquiry".
A legal challenge launched by Mr Drumgold found Mr Sofronoff might have been influenced by Ms Albrechtsen's publicly expressed views and his behaviour gave rise to a reasonable apprehension of bias.
But the court upheld the majority of the inquiry's findings Mr Drumgold had sought to have overturned.Â
The inquiry followed the prosecution of former Liberal staffer Bruce Lehrmann, accused of raping his then-colleague Brittany Higgins in a ministerial office at Parliament House in 2019.
His 2022 criminal trial was abandoned with no verdict because of juror misconduct and prosecutors opted not to hold a re-trial.
But in a defamation case Lehrmann brought against media companies which published the allegations, Federal Court Justice Michael Lee found on the balance of probabilities that Lehrmann raped Ms Higgins.
Lehrmann is appealing against the April ruling while facing trial in Queensland over separate rape allegations.
