Former public trustee Peter Carne won an appeal in the Supreme Court earlier this month, which stopped the Crime and Corruption Commission report from being tabled in parliament.
CCC chair Bruce Barbour says that decision sets a concerning precedent for transparency, so an appeal must be lodged in the High Court.
"If if the current decision were to stand, then there would definitely be concern ... of what we would be able to do in the future in terms of being open and transparent about our investigations and what we conclude in relation to the investigations," he told a parliamentary committee on Friday.
Mr Carne was suspended in June 2019 when the CCC launched an investigation into allegations levelled against him and later resigned.
The watchdog forwarded their report to the Parliamentary Crime and Corruption Committee, asking them to give it to the Speaker.
That would allow the report to be published and allegations protected by parliamentary privilege, preventing Carne from taking any defamation action.
He tried to stop that from happening in the Supreme Court, saying the report's publication would breach his human rights and deny him procedural fairness.
He lost the case in September 2021 but challenged the ruling in March.
Two of the three appeal judges ruled in Carne's favour on August 5.
Justices Philip McMurdo and Debra Mullins allowed the appeal, setting aside the original ruling and ordering the CCC to pay Carne's costs.
However, Justice Paul Freeburn said his case should be dismissed.
"It is not a report which has been made by the Commission in the performance of any of its statutory functions," the decision said.
"Consequently, this report could not be the subject of parliamentary privilege."
Mr Barbour said if that decision had stood earlier, it would have also prevented the publication of other CCC reports into matters of public interest, such as its recent probe into a laptop involving the Integrity Commissioner and the Public Service Commission.
He said it was important that CCC investigations are made public to clarify and correct the record.
"So clearly, there are very significant ramifications, and that decision (Carne) is inconsistent with the way we and our predecessors have practised business in the corruption area for a long time," he said.
"That's why it's important for us to seek a review."
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