Northumbria Police have released CCTV images of legal high users stumbling around, falling over and collapsing unconscious on a city centre's main shopping street.
Different users were caught on camera weaving in and out of shoppers, in Northumberland Street, Newcastle, barely able to put one foot in front of the other, and sometimes hitting the pavement.
The problem in the city was so bad Northumbria Police, the city council and ambulance chiefs set up a "New Psychoactive Substances" taskforce in January.
Already the number of call-outs by police involving legal highs has dropped by half, and by almost two-thirds to the ambulance service, in the first month the task force has been running.
Police and Crime Commissioner Vera Baird said the issue is a "top priority" and explained the aim was to disrupt the sale of legal highs.
Work has included undercover test purchases, executing search warrants and warnings being issued to shops threatening prosecution if they continue to sell them.
There has also been educational work about the dangers of legal highs.
Superintendent Richard Jackson said: "The aim of the task force was to find those responsible for selling legal highs and do as much as we could to make life difficult for them to do so.
"The feedback we are getting from the streets is that legal highs have become harder to buy than ever before."
Simon Swallow, head of resilience and special operations at North East Ambulance Service, said: "We are urging people not to take these so-called legal highs as they are putting their own lives in danger and also endangering the lives of others.
"These calls are potentially delaying our response to someone else who is suffering a heart attack or other life-threatening condition."
Coun Nick Kemp, of Newcastle City Council, said: "Legal highs are a real and present danger to anyone who takes them, and as far as I am concerned the legislation that bans them can't come quick enough."
"I hope that communities remain vigilant and contact the authorities if they see anyone dealing in them.
"The council will not hesitate to issue warning letters to those dealing in them as we can never be complacent about something as dangerous as legal highs."