"This is a quick way to get rid of the rough sleepers and I don't think it is acceptable. I don't think it is the type of Auckland we would like to design," said Casey, a City Vision councillor who has long campaigned for the rights of the poor and vulnerable.
Auckland Chamber of Commerce chief executive Michael Barnett said what ACG Senior College and other businesses were doing with sprinklers was wrong, but they were acting out of frustration at the lack of action by council on the issue of homelessness.
He said there was a problem with young people early in the morning acting in an intimidating way.
Casey said there were a range of factors at play for people sleeping rough and causing a nuisance in the city, from drunk men urinating in public to beggars who might not be homeless to drug dealers in back doors.
"This is a sledgehammer to crack a nut and the last response being used first," Casey said.
"According to the advice I got there is nothing in the [council] regulations that prevents it. We can't ask them [building owners] to take them down without there being good reason. They are in a private space.
"My plea to the businesses is to take them down," Casey said.
The council, she said, was very happy to talk to any businesses which have an issue with rough sleepers.
According to the Auckland City Mission, the number of rough sleepers in the central city doubled to 228 between 2015 and 2016.
The Herald has gone to ACG Senior College for comment but not received a response at the time of publication.
In March, the Government launched an "end homelessness in Auckland" pilot that aims to get more than 400 people off the streets.
It has teamed up with Auckland Council and community social housing providers on a two-year pilot that has the lofty goal of ending homelessness in greater Auckland.
It aims to help 472 chronically homeless people find accommodation during two years.
