Fallout from the West Australian Corruption and Crime Commission being handed sensitive emails belonging to three former upper house MPs could lead to contempt proceedings, including against the watchdog's boss.
The CCC was provided with the emails - including those from whistleblowers and constituents - as it probes the use of parliamentary electoral allowances.
As the investigation is ongoing, it shouldn't have yet been made public, but was revealed by the Procedures and Privileges Committee as it reported two top bureaucrats had defied its wishes regarding surrender of the documents.
Department of Premier and Cabinet director general Darren Foster was accused of a seemingly "extremely serious intentional breach of parliamentary privilege".
That was because he used State Solicitors Office staff to identify which documents should be excluded on the basis of privilege, rather than provide them to the committee.
"Mr Foster's procedure was not authorised by the committee or this house and he was expressly advised of that fact when the committee first became aware of his intentions," committee chair Kate Doust said.
"Mr Foster chose not to follow the committee's procedure."
She said that conduct "sowed the seed" for the department's acting director general Emily Roper to refuse to comply with a summons to deliver the MPs documents to the committee.
As the committee undertakes its own investigation into the controversy, CCC commissioner John McKechnie has been summonsed to appear before it at a private hearing.
In a letter he sent to Attorney General John Quigley that was tabled in parliament on Thursday, Mr McKechnie expressed concerns because he may be asked to disclose official information.
He may also be asked to disclose information about a current investigation, and both are in breach of the Corruption Crime and Misconduct Act.
"I am concerned that the committee may institute proceedings for contempt of parliament," the former Supreme Court of WA judge wrote.
"In that event, I will seriously consider my future leadership as I put the interests of the commission well above my own.
"It would be wrong for the commission to be vilified for fearlessly carrying out its functions."
Separately, Premier Mark McGowan backed Mr Foster after Liberal MP Zak Kirkup called on the him to stand the bureaucrat down until after the committee completes its investigation.
Mr McGowan flatly refused.
"Absolutely not," he told parliament on Wednesday.
"I think that we should support inquiries into corruption, not attack them."
Liberal Democrats MP Aaron Stonehouse said he was deeply concerned by the revelations in the report.
"Members of parliament cannot do their job properly if we have looming over our head the threat of unelected bureaucrats reading our emails to and from constituents," Mr Stonehouse said.
"There is an obvious potential for a conflict of interest when the people who are running the state are able to access the emails of those who, like me, are meant to hold them to account."