Two of Western Australia's most senior public servants, including the head of Premier Mark McGowan's department, face being held in contempt of Parliament over actions described as shocking and striking "at the heart of our democratic institutions".

Key points: Kate Doust is sharply critical of two senior public servants in the Premier's department

Kate Doust is sharply critical of two senior public servants in the Premier's department She says department head Darren Foster intentionally breached parliamentary privilege

She says department head Darren Foster intentionally breached parliamentary privilege Premier Mark McGowan has defended Mr Foster in Parliament on Wednesday

A report by the Procedures and Privileges Committee has also revealed the Corruption and Crime Commission (CCC) is investigating three former members of the Legislative Council.

In a damning assessment of the conduct of Darren Foster, the director general of the Department of Premier and Cabinet, the report said he was responsible for "prima facie, an extremely serious intentional breach of parliamentary privilege".

The department's acting director general Emily Roper could also face sanction after it emerged she refused to comply with a summons issued by the committee to hand over thousands of emails and documents belonging to the three former MPs and their staff, as part of the CCC investigation.

In a statement to Parliament, Legislative Council president and Labor MP Kate Doust was sharply critical of her leader's department, saying Ms Roper's "cavalier disregard" of the committee's right to the documents was shocking and appalling.

Legislative Council president and Labor MP Kate Doust has been highly critical of her leader's department. ( ABC News: Hugh Sando )

According to the committee's report, the CCC had since April issued the Department of Premier and Cabinet two notices to produce over three years' worth of emails and attached documents sent via the parliamentary email accounts of three former MPs and their staff.

The privileges committee then developed a method to deal with how the CCC could access these documents without breaching the privileges of the Legislative Council.

But the report said that in late June, the Department of Premier and Cabinet advised the committee it had devised its own way of identifying privileged documents "that it intended to follow in order to expedite the production of the documents to the CCC".

The report said even though Mr Foster was warned he and his staff risked being in contempt of Parliament, he and his staff nonetheless went ahead with their own sorting process, sending only certain documents to the CCC.

Ms Doust said only the Parliament or its authorised delegate could determine if documents were subject to parliamentary privilege, and not Mr Foster or his staff.

"These two related matters of privilege and their effect on the sources of information to the Parliament and its members strike at the heart of our democratic institutions," she said.

The privileges committee then decided to conduct an audit of which documents the department had sent to the CCC. It issued a summons to Ms Roper, in Mr Foster's absence overseas, to appear before the committee and produce copies of all the documents provided to the corruption watchdog.

Premier Mark McGowan commended Mr Foster's actions and rejected calls for him to be sacked. ( ABC News: Rhiannon Shine )

But Ms Doust said Ms Roper refused to do so.

In Parliament on Wednesday, Mr McGowan defended Mr Foster and rejected Opposition frontbencher Zak Kirkup's call for him to be sacked.

"I commend Mr Foster on what he has done. He has cooperated with the CCC against potentially corrupt action by former members of Parliament," Mr McGowan said.

"I commend what he has done and I think you need to read the report a little more deeply before you come in here defending potentially corrupt action by former members of Parliament."

The committee's report acknowledged that making the issue public could prejudice the ongoing CCC investigation.

It also acknowledged the potential reputational harm to the three former Legislative Council MPs, "despite the absence of any finding of misconduct against them by the CCC, and no criminal charges having been laid".