"We're seeing a lot of cars which have people inside them holding large flags out the window.
"Many of those are young children and if there's an accident, that flagpole could hit them easily."
The makeshift flagpoles were also a potential hazard.
"They're taping things on and especially with the windy conditions, you can imagine a flag could easily fly off and hit another car and cause an accident."
Another issue is the number of people cramming into the one vehicle during particular days of celebration. Police reiterated the message that each person must have a seatbelt on.
Mr Maea encouraged members of the public to continue to support their favourite team without the large flags on cars. The popular smaller car flags were still okay, he said.
The message has been sent to members of the Pacific community and police are asking people to spread the word through various networks, including on Pacific radio stations and at church services.
Tongan community leader Salote Lilo said she understood why the police had finally brought up the issue, as some cars were becoming obvious hazards on the road.
"We couldn't believe it at first. They go out of their way to get big things and attach it to their towbar. It's fun, but can be dangerous."
Mrs Lilo has four small flags - the Tongan, Samoan, Fijian and New Zealand - attached to her car.
