A man was tasered 13 times in a Perth watchhouse as nine police officers stood by, Western Australia's corruption watchdog says.
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 unevenly against Aboriginal people.
The commission said tasers were increasingly used to force offenders into compliance rather than as an alternative to firearms to reduce injury, as originally intended.
Its director of corruption prevention, Roger Watson, said tasers had become the police weapon of choice. 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 use in 2007 to 43 per cent last year.
In that time there also was a fourfold increase in the use of tasers to threaten people.
"Examples of this are highlighted in the report, which includes video footage of an incident at East Perth watchhouse 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 have a mental illness or be affected by substance abuse, and had removed his belt and earring for officers but refused to have a strip search.
After an internal police investigation, two police officers were disciplined for using undue and excessive force and two senior officers were found to have provided inadequate supervision.
WA Premier Colin Barnett said the man was not co-operating with police but was not acting violently.
"It was excessive use of a Taser that could not be justified," Mr Barnett said.
He said he thought "nine fit young men" could have restrained the man more appropriately.
Acting Police Commissioner Chris Dawson said: "It was wrong, it's unacceptable, it was alarming when I looked at it and it'll be alarming when the public view it."
But he said it was not typical of police use of tasers and since the incident not one of the 25,000 detainees who had passed through the watchhouse had been Tasered.
Mr Dawson said the fined officers were "fortunate not to be sacked", but the tasered man had opted not to pursue criminal charges.
A second case highlighted in the 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 commission also expressed concern about the unbalanced use of tasers against Aborigines, increasing from 16 per cent in 2007 to 30 per cent last year.
It was also concerned about taser use against people with mental illness and drug users.
The report found the majority of taser use by police was reasonable and they were effective weapons.
The commission made 10 recommendations, including that tasers only be used by police when there was an imminent threat of serious injury.