"Hoax calls cost lives," is the message from PC Lee Thomas of Newport's Safer Neighbourhood Team.
Pranksters made three hoax 999 calls from a phone box situated outside B&M in Newport's High Street, all on the afternoon of last Sunday, May 17.
The emergency services had to respond as if the calls were genuine, tying them up and meaning they were unavailable to deal with any real emergencies that could have occurred.
PC Thomas said that wasting the time of police and other emergency services could have unforeseen consequences including more fast traffic on the roads as crews respond to the reports.
He said: "Hoax calls not only tie up emergency phone lines, making it more difficult for people reporting genuine emergencies to get through, but they also waste the time of all emergency services, not just the police, as the relevant service has to respond as if it is a genuine call.
"It also increases the potential risk to other members of the public as it means emergency vehicles will be travelling at higher speeds than normal traffic to reach the supposed incident location, with everything that can entail.
"This is not the first time we have had this problem in Newport recently and we would appeal to parents and carers to make sure their children are fully aware of the risks and dangers that can be posed by their irresponsible activities."
Anyone with any information on who made the hoax calls is encouraged to report it, by contacting the Newport Safer Neighbourhood Team by email at firstname.lastname@example.org.
Alternatively, report information to Crimestoppers anonymously using their telephone number 0800555111.
The number of hoax calls made to the West Midlands Ambulance Service has averaged at about 1,000 a year in the past six years.
Last year Jeremy Brown from the ambulance service warned that "quite a lot" of hoax calls are made by children and young people.