The Corruption and Crime Commission, in a report tabled in state parliament, said the incident highlighted police officers' wrongful use of the Taser stun gun.
It also said the weapon was being used disproportionately against Aboriginal people.
The CCC said Tasers were increasingly used to impose compliance by alleged offenders rather than as an alternative to firearms to reduce injury, as originally intended.
The commission's director of corruption prevention, Roger Watson, said Tasers had become the police weapon of choice, representing 65 per cent of reported use by the WA force in 2009.
The use of other options such as capsicum spray had significantly decreased since Tasers were introduced in 2007, the report found.
Mr Watson said they were increasingly being used against people resisting arrest, up from 20 per cent of Taser deployments in 2007 to 43 per cent in 2009.
There was also a four-fold increase over that period in the use of Tasers to threaten people, he said.
"Examples of this are highlighted in the report, which includes video footage of an incident at East Perth Watch House where Taser weapons were deployed eight times against an unarmed, non-threatening man surrounded by nine police officers,'' Mr Watson said.
"Taser weapons were deployed against him a further five times off video.''
The report found the man's actions indicated he was likely to be suffering from a mental illness or from substance abuse and had removed his belt and earring for officers but refused to undergo a strip search.
Following an internal police investigation, two police officers were subject to disciplinary charges for using undue and excessive force and two senior officers were found to have provided inadequate supervision.
A second case highlighted in the CCC report concerned a man who was tasered while running from police officers, causing him to fall and break a tooth.
He was tasered twice again while on the ground and seemingly not posing a risk to the male and female officer trying to apprehend him.
The male officer said he had tasered the man again because he thought there was a threat of injury as he did not feel safe when accompanied by female officers.
The officer was counselled on his attitude to fellow police officers.
The CCC also expressed concern about the disproportionate use of Tasers against Aboriginal people, increasing from 16 per cent in 2007 to 30 per cent in 2009.
It was also concerned about the Taser use against people with mental illness and drug users.
The CCC report found the majority of Taser use by police was reasonable and they were effective weapons.
It found that police use of firearms had doubled in the two years since the introduction of tasers and injuries to police officers had increased by 22 per cent in the same period.
The CCC made 10 recommendations, including that Tasers only be used by police when there was an imminent threat of serious injury.
The commission says that would bring the use of Tasers in WA into line with other Australian and international police jurisdictions.
There have been no reported deaths from Taser use in WA.
Every frontline police officer in the state has been armed with a Taser and their use has been defended by Commissioner Karl O'Callaghan as a safer alternative to shooting offenders with firearms.
He announced in May that WA Police would not be introducing Taser Cams, as a trial proved the cameras would be a waste of money.
WA Premier Colin Barnett said video footage of the incident in the East Perth watchhouse was disturbing.
He said the Aboriginal man was not cooperating with police but was not acting in a violent manner.
"It was excessive use of a Taser that could not be justified,'' Mr Barnett said.
"I think anyone seeing that footage would find it totally unacceptable.''
The premier said he thought that "nine fit young men'' could have restrained the man in a more appropriate manner.
It was a very serious incident and a major breach of procedure, he said.
"I think it's something that cannot be swept under the carpet,'' the premier said.
