A man attacked a traffic warden with his key in Hove, leaving the warden needing hospital treatment for a minor eye injury.
The assault in Church Road, Hove, happened as the warden was issuing a ticket because the van was parked on double yellow lines.
A 33-year-old man from Brighton has been arrested on suspicion of assault causing grievous bodily harm (GBH).
He has been bailed until Tuesday 15 March.
The warden was entering the details into his handheld computer when he was approached by his attacker.
The man pressed his key against the warden’s face and flicked it up.
The victim was taken to the Royal Sussex County Hospital in Brighton for treatment.
PC David Elliott, of Sussex Police, said: “We are offering our support to the victim, who has been left clearly shaken by the assault.
“I am keen to speak to anyone who witnessed the assault.”
Tim Cowen, from NSL, the parking contractor which employs the warden, said: “Civil enforcement officers, sometimes known as traffic wardens, are public servants and should not have to put up with being assaulted just for doing their job.
“We are grateful for the prompt response from Sussex Police and hope that there are witnesses who might help them catch the person who did this.”
The attack happened at about 4.10pm on Friday 18 February.
Anyone with information is asked to contact Sussex Police on 0845 6070999 or to call the independent charity Crimestoppers anonymously on 0800 555111.