Police have acknowledged the report's findings, but Acting Eastern District Commander Inspector Andrew Sloan said the man posed a serious threat to officer safety, and force was necessary to control the situation.
"When first challenged by police the offender fled from a vehicle in which a firearm was located and officers were rightly concerned he was carrying a second, concealed weapon," Inspector Sloan said.
"The man, wanted for a series of serious offences across multiple districts, went to great lengths to evade police and repeatedly failed to comply with officers' instructions," he said.
The IPCA report said the man was arrested in the early hours of January 18 last year, after police spotted a car with a firearm on the back seat.
The man got out of the car and fled on foot.
Police with a dog tracked him for several hours, eventually finding him on a fenced construction site about 4.30am.
During his arrest, the man was pepper-sprayed twice.
One officer, identified as Officer A, ran at and jumped on Mr X's back, pinning him to the ground with his knee.
The man held his arms underneath his body to prevent himself from being handcuffed.
Officer A punched him several times to get him to release his arms.
The man sustained serious injuries including a punctured right lung, fractured ribs, a fractured neck vertebrate, and a cut on his scalp.
The IPCA report said there were enough officers present to deal with the resistance the man offered to his arrest.
"In addition, the low likelihood of the perceived risk meant that the level of force used by the officer was ultimately unreasonable," the report said.
"We accept Officer A thought Mr X might have had a concealed weapon on him," IPCA chair Judge Colin Doherty said.
"However, in this case, we find the risk of that was low, and not imminent.
"The officer caused significant injuries, and the degree of force employed was disproportionate to the risk Mr X posed by his actions in kneeling or lying down."
Mr X believed that his scalp injury, which required stitches, was caused by being stomped on. However, the authority found that it was probably caused by contact with a metal drainage grate with a sharp edge in the ground.
Sloan said it was unfortunate when police had to resort to using force, and the man's injuries were "regrettable".
"Every day, Police staff are faced with challenging situations that require them to act decisively," he said.
"Safety — of the public and our own people — is at the forefront of these decisions."
The man initially refused medical treatment but ambulance staff treated him at the police station and said he did not need to go to the hospital straight away. He was taken to hospital after his identity had been established.
The man was eventually found guilty on a charge of resisting arrest.
In the car, police found a .22 calibre rifle and ammunition, a radio scanner, a small amount of cannabis, a methamphetamine pipe, and other drug-related items.
