The Police watchdog's found an officer wasn't justified in punching a man being arrested at an Auckland road block

The intoxicated man was stopped riding his bicycle without lights and incorrectly wearing his helmet in March last year.

He was arrested and searched after being aggressive and trying to leave when asked for his details.

During the search an officer punched him in the cheek, believing he was about to spit on him.

The Independent Police Conduct Authority says it was excessive use of force.

Police accept a punch wasn't the best option and the officer should have used an open hand to push away the man's face.