Corruption and Crime Commission officers used assumed identities to obtain multiple driver's licences so they could rack up demerit points with impunity, the parliamentary inspector has found.

As part of Michael Murray's ongoing investigation into the CCC's Operational Support Unit (OSU), he has discovered officers have used assumed identities to obtain driver's licences in the ACT and Tasmania, then have the domicile changed to WA.

"No law authorised the Commission to use either means to achieve the outcome of a driver's licence issued in this state under a Commission officer's assumed identity," Mr Murray said in a report on Friday.

He also found some officers had accumulated - and were continuing to amass - enough demerit points for traffic offences to trigger a driver's licence suspension, but were using multiple licences under various aliases to avoid that happening.

"This systemic abuse of the assumed identity power resulted in a situation where OSU officers would have been driving Commission vehicles on the state's roads without the legal right to do so," Mr Murray said.

CCC officers who weren't in the OSU also possessed multiple driver's licences under various names, he discovered.

And after it emerged an OSU officer had been charged and fined for possessing a prohibited drug at a music festival before applying for the role of special constable, Mr Murray found out that the CCC had never checked the criminal history of any officers before such applications were made on their behalf.

Mr Murray said it was not necessary to make recommendations in relation to criminal history checks because new procedures had been introduced in that respect, but he made other recommendations.

They were that a Commission officer should only hold one assumed identity at any time and should notify the Department of Transport in writing about any demerit points or fines imposed under an assumed identity so they can be recorded against the officer's real name.

The CCC said it had already dealt with issues raised in the report.

"The CCC worked co-operatively with police during the investigation and have since made considerable changes including implementing policies and processes for dealing with demerit points accumulated on assumed identities," it said.

"The officers whose actions gave rise to the investigation and report are no longer with the CCC."