An advocacy group for renters is worried a database used by landlords to screen and rate tenants could be abused.
The Tenancy Information New Zealand database allows landlords to rate tenants at the end of their tenancy and see how other landlords have rated applicants.
Tenancy Information spokesperson Ian Barker said the organisation was very careful to keep comments about tenants out of it because they could be so subjective.
There was a simple system using boxes to rate the tenant on a range of issues such as paying rent, keeping the dwelling tidy and being considerate of neighbours, he said.
Mr Barker said the boxes ranged from good to below average, which is the worst that could be recorded.
The information stays on the database for six years.
Renters United spokesperson Kayla Healey told Nine to Noon the service gave landlords all the power.
"We want to know what they're doing to ensure that this database of theirs isn't being used as a threat to tenants and also about this objective information that's provided on people," she said.
"We really do wonder what checks are in place to make sure landlords aren't loaded information about people because they don't like them."
Tenancy Information said tenants could ask to see the information about them on the database and challenge ratings.
It said tenants consent to being on the database when they apply for a property.