A West Australian man with a disability who was strip searched and prosecuted after a false claim he was photographing children should receive an apology from WA Police and have his conviction expunged, according to one of the state's top oversight bodies.

Key points: The man was arrested over reports he was taking photographs of children

The man was arrested over reports he was taking photographs of children A strip search found the man had no device capable of taking a photograph

A strip search found the man had no device capable of taking a photograph He was convicted and fined for failing to provide police his details

A scathing report from Michael Murray, the parliamentary inspector to the Corruption and Crime Commission (CCC), blasted WA Police's handling of the matter, saying the force had previously been advised the arrest was unlawful but chose not to act on that finding.

Mr Murray's report, released in State Parliament on Thursday, found Denys Martin was arrested in Cottesloe in 2017 after witnesses said they saw him taking photos of children.

But after a strip search at a police station, it was confirmed he did not possess a mobile phone, camera or any device capable of taking a photograph.

Mr Murray stated it seemed Mr Martin was "pretending to photograph cars which appeared to him to be exceeding the speed limit", as a warning to drivers.

Mr Martin was taken into custody and forcibly fingerprinted in an attempt to identify him, before being convicted and fined $500 for failing to provide his details.

'There was absolutely no evidence'

An initial police investigation into those events found his complaints were "unsubstantiated", but that probe was reopened and a "senior police solicitor" recommended he be given a formal apology and assistance to appeal against his conviction.

"However, the police decided to obtain independent legal advice … and police arrived at the conclusion that the arrest was lawful and that no remedial action was required," the report stated.

Michael Murray says the state should help Mr Martin appeal against his conviction. ( ABC News )

Mr Murray attacked that decision in his report.

"Mr Martin should not have been arrested and there was no basis to require him to provide his personal details," the report stated.

"He had done nothing wrong.

"There was absolutely no evidence … that he was photographing children or was doing so to capture images of their underwear.

"He should not have been prosecuted for this offence."

CCC's response also questioned

The report recommended the state assist Mr Martin in an appeal or pardon him through the Executive Council.

It also called for his fine and costs to be repaid and for an apology to be issued.

The CCC initially dismissed Mr Martin's complaint. ( ABC News: Benjamin Gubana )

But Attorney-General John Quigley said he would not be intervening in the case, citing Mr Martin's guilty plea.

"I do not think the state has any scope to act once a citizen goes to court and pleads guilty to an offence," Mr Quigley said.

"How can the state then get in there and give compensation or rectification?"

Mr Quigley said Police had received advice supporting the arrest.

WA Police have been contacted for comment.

The report also questioned the CCC's handling of Mr Martin's mistreatment complaint, which was initially dismissed before the matter was raised with the parliamentary inspector.

It came as a parliamentary committee launched an investigation into the CCC's handling of complaints about excessive use of force by police officers.