The Independent Police Conduct Authority has found a police officer unjustifiably and unlawfully used pepper spray on an arrested man in a cell last year.

The intoxicated man had crashed his car on June 23 and was brought back to the station, but was aggressive towards officers who attempted to restrain him.

After the man was placed in the cell by eight officers, one went back in after noticing a pair of handcuffs on the floor and their leg was grabbed by the arrested man.

A second officer entered the cell and pepper sprayed the man in the face and he immediately let go of the leg.

The second officer accepted that it could have been possible to drag the first officer out of the cell, but maintained his use of pepper spray.

He stated that pulling the first officer out of the cell would have increased the risk of harm to those involved.

"I take a lot of pride in my decision-making and if I could go back I'd do the same thing. I still think even in hindsight I made the correct decision," he said.

But authority chairman Judge Colin Doherty deemed that the officer's use of pepper spray was unnecessary and was "an excessive use of force".

"The officer was focused on subduing the man with the use of pepper spray, which came at the expense of good, sound, decision-making in accordance with Police policy and best practice," he said.

The authority reported that a lower level of force should have been applied before resorting to the use of pepper spray - some staff witnesses to the incident agreed.

Other staff members supported the second officer for using pepper spray on the basis that his actioned enabled officers to exit the cell safely without having to engage physically.