WA's corruption watchdog says new vision showing a police officer hitting a man in the head seven times, released as part of its investigation into excessive use of force, "speaks for itself".

Key points: A man described as "Mr Wells" was arrested in Fremantle's High Street mall

A man described as "Mr Wells" was arrested in Fremantle's High Street mall He was wrestled to the ground, hit and handcuffed by a group of officers

He was wrestled to the ground, hit and handcuffed by a group of officers The CCC says the force used to over come him was "excessive"

The Corruption and Crime Commission report into an incident in Fremantle in September 2017, tabled in the WA Parliament on Thursday, made findings of misconduct against two officers.

The events of that night were captured on CCTV in the High Street mall, with vision showing a man, described as "Mr Wells", trying to light a cigarette while in discussion with some police officers.

A police auxiliary officer tries to grab the cigarette, sparking a struggle which led to Mr Wells being wrestled to the ground, subdued using an open-hand technique and handcuffed.

The report said the most senior police officer on the scene, Sergeant Nathan Trenberth, repeatedly punched Mr Wells in the head while he was on his back.

It is also alleged that after he was handcuffed, Mr Wells's finger was bent back and dislocated.

"The force used to overcome Mr Wells, in the Commission's opinion, was excessive," the report said.

"Mr Wells was intoxicated and no doubt difficult, but the triggering event for the incident was the snatching away of his cigarette … Until then he had shown no overt aggression."

The incident occurred when the man lit a cigarette while being questioned by the officers. ( Supplied )

'Disturbing' inconsistencies

The report was particularly critical of the "disturbing" inconsistencies between witness statements from police and the CCTV vision.

For example, the most senior police officer involved — Sergeant Trenberth, who has since resigned from the WA Police force — said Mr Wells was "aggressive" and "vengeful" towards police.

"CCTV footage does not support Sergeant Trenberth's insistence that Mr Wells was displaying continued aggressive behaviour towards the officers," the report said.

The report also raised concerns with the treatment of Mr Wells after he was taken back to an observation cell at Fremantle Police Station.

He was kept handcuffed for longer than an hour and, after he complained about his treatment, was told:

"You're the one that kicked me in the head and you kicked another police officer in the head, so we've kicked the shit out of you."

Internal investigation launched

The report said Mr Wells was later charged with obstructing public officers, three counts of assaulting a public officer and one count of failing to comply with a lawful order, but his prosecution was later discontinued.

Mr Wells did not want to make a formal complaint but WA Police started an internal investigation into the incident, leading to two officers — Sergeant Trenberth and Constable Julian Donohoe — being stood down.

Sergeant Trenberth has since resigned and Constable Donohoe was charged with assault occasioning bodily harm last week.

He will appear in the Fremantle Magistrates Court on March 26.

Do you know more about this story? Email turner.rebecca@abc.net.au

Police Commissioner Chris Dawson said he took seriously any allegations of excessive use of force.

"Police have a lawful authority to use force," he said.

"It's part of our job. We exercise force every day and have for many, many years, and will continue to do so. What I have to do as Commissioner is ensure that the lawful force is used."

The internal investigation is continuing.