The police arrested the man in Newhaven town centre
A police officer has been filmed "punching" a member of the public he was trying to arrest.
The man had been found lying on the ground in Newhaven town centre in East Sussex at about 18:30 GMT on Friday.
Ch Insp Rosie Ross of Sussex Police said: "We are aware of the video. It has been referred to our professional standards department for review."
She said techniques used during arrests "may appear very robust" and no formal complaint had been made.
She said: "It is important that the risk of injury to the suspect, the public and the officers themselves is kept to the minimum and approved techniques may appear very robust.
"However, we will ensure that this incident is investigated to satisfy ourselves that the actions taken were appropriate."
A 40-year-old man has been charged with being drunk and disorderly and assaulting a police officer.
The arrest was filmed by a passer-by
