A man has been charged with impersonating a police officer after he allegedly arrested and attacked a prostitute in Perth.

It is alleged the 25-year-old man from South Perth met a prostitute at a city hotel before claiming he was an Australian Federal Police officer.

Police say he told the woman she was under arrest before restraining her and assaulting her with a replica firearm and a kettle.

They were alerted when hotel staff reported a disturbance in the room.

Officers say they found a replica firearm, a knife and a police-style vest in the room.

The man has been charged with several serious offences including deprivation of liberty, assault, and unlawful wounding.