Retailers need stronger powers to protect staff and customers from violent repeat offenders, Retail NZ says, amid reports of rapidly escalating aggression.

The Justice Select Committee is recommending by majority that The Trespass Amendment Bill be passed into law.

The bill would give retailers the power to trespass people from multiple sites, double fines to $2000 and increase the maximum trespass period to three years.

Retail NZ chief executive Carolyn Young said violence in stores was on the rise, with people becoming more agitated and entering businesses with concealed weapons.

"They will come in with knives, with hammers, with screwdrivers, with machetes ... Some stores within their stores sell things that can be turned into a weapon ... People will come in to a hardware store and use things on their shelves to threaten staff to be able to steal goods or do harm to people," she said.

"We have also seen guns that have been presented in certain circumstances, and all of those things mean that it's not a safe environment for staff members or customers."

Young said clear guidance would be needed to ensure new powers were used appropriately.

'Not convinced' - Labour and Greens

Opposition parties have raised concerns about the proposed changes, while questioning if harsher penalties would work as an effective deterrent to retail crime.

Labour said that despite some improvements to the bill, it remained concerned about the proposed scope of multi-location trespass notices.

"We remain concerned that there will be situations when vulnerable individuals may be unable to access essential goods and services due to the scope of these notices.

"We are also not convinced that the increase in penalties will act as an effective deterrent and consider there are other policies that may more effectively address the drivers of crime," it said.

The Green Party said it did not support the bill and remained concerned that the increase in fines from $1000 to $2000 would be "unrealistic" for offenders, who often resorted to retail crime as a result of the cost-of-living crisis.

"It is important that we have the right balance between clarity for retail stores and safety of retail employees and owners. However, we do not believe this will result in the expected effect of deterrence for retail crime," it said.

"The Green Party firmly believes that if we want to address the issues of retail crime, we must address the root causes."