PC Robert Dovey had been called to reports a man was being violent and abusive towards officers - one of whom was the police officer's partner - following an incident in Horbury, Wakefield.
Police at the scene had to use pepper spray to get the man under control and issued a 'code zero alert', before he was handcuffed twice and put into the back of a police van, following the melee on December 9, 2017.
PC Dovey is alleged to have arrived at the scene and shouted "Get him out and put him in my van", to which the prisoner did not respond.
Giving evidence at a misconduct hearing, held at the force's headquarters on Monday, Matthew Holdcroft said: "PC Dovey jumped in the rear of the van and without any warning punched the man in the face with his right hand.
"Sergeant Dent tried to pull him away. He had thrown six or seven punches before he got out the van.
The misconduct hearing heard how the prisoner shouted "police brutality" and asked PC Dovey what he was doing when the officer hit him twice on the head.
Mr Holdcroft said: "Sgt Dent and PC Dovey transported him to the van and they had got to Horbury Road when PC Dovey said 'we need to pull over somewhere quiet and give this guy a good hiding'.
"Sgt Dent said this was not going to happen and told him to get him to custody quickly.
"They had reached the Normanton bypass when PC Dovey said 'there is somewhere down there where we can go and give this guy a good hiding'.
"Sgt Dent again refused and told him to get to the police station."
The panel also heard PC Dovey was acquitted of common assault following a trial at Leeds Crown Court on July 26, this year.
PC Dovey is alleged to have breached the Standards of Professional Standards in relation to Use of Force, Authority Respect and Courtesy and Discreditable Conduct.
It is alleged he used force that was not deemed reasonable, necessary or proportionate on a member of the public who had been detained by other officers.
It is also alleged that the officer moved the member of the public into another van to give the officer the opportunity to assault him further during the transfer and during the journey.
PC Dovey denies the allegations of misconduct.
In mitigation Richard Holland said the police officer states he was at the scene to collect the prisoner and take him into custody.
He accepts punching the prisoner once but stated it was in self-defence.
The hearing continues.