Not everyone is convinced a new bylaw will keep Christchurch's windscreen washers at bay.

The Christchurch City Council has voted unanimously to give police the authority to seize windscreen washers' equipment and prosecute them under the council's public places bylaw.

The bylaw prohibits people from undertaking commercial activities in public places without first obtaining a permit from the council. The bylaw has been flouted by the city's roadside windscreen washers, most of whom are youths.

A successful prosecution under the bylaw could result in a fine of up to $20,000 being issued and a conviction being recorded.

Christchurch Mobil franchisee Hemal Besai said he was not sure if the bylaw would make a difference to the window brush thefts that kept happening at his sites, because the culprits were so young.

"Every time they have stolen from me I haven't seen one that looked over 15 . . . they should be in school not cleaning people's windows."

Sergeant Todd Webley, from the Phillipstown Neighbourhood Policing Team, said if a youth under 16 was caught breaking the bylaw they would likely be dealt with by the police's youth aid section rather than through the courts.

They would be brought before the court only if they were already facing other serious charges, Webley said.

"We are expecting there will be a small percentage of hardcore [windscreen washers] who will keep doing this . . . but that's the group we want to target."

Besai said he had been keeping his window brushes inside for the last month because of the thefts and would continue to do so.

"One time they [window washers] tried to wash a car right on the forecourt, when the customer said no they hit the car with the brush and ran away, but the police caught them and brought the brushes back to me."

Another garage owner said he was happy the bylaw had been introduced because he had brushes stolen at least once a week.

"Our brushes are green so when you see them [window washers] at the traffic lights with green brushes you sort of know where they got them from."

Police have received reports in recent months of windscreen washers shoplifting, stealing tools from service stations and assaulting people.

In one incident a driver had his side mirror kicked off by a window washer when he said he did not want his window washed. When he stopped the car and confronted the window washer he was set upon by a group of six or seven youths.

Police were powerless to do anything about the windscreen washers until fights broke out or formal complaints were laid by members of the public.

Police believed some of the window washers have pocketed big bucks through their illegal trade, with some earning between $60 and $70 cash an hour.

Read more

* Gangs 'running' windscreen washers

* Illegal windscreen washers earning big bucks in Christchurch

* Windscreen washer tired of bad rap

Cr Yani Johanson said after viewing police footage of what was happening at the intersections where the windscreen washers were working he appreciated how frightening their behaviour could be for motorists and how dangerous it was for windscreen washers themselves.

"The evidence is pretty compelling; we have to act on this issue," Johanson said.

"At the risk of sounding heartless this is a no brainer," Cr Ali Jones said. "These kids are at risk of hurting themselves, or hurting others."