A tenant chief says landlords "can post anything they like" on blacklists they share, yet there was no recourse for people who rented properties against such lists.
Penny Arthur, the Christchurch-based manager of the Tenants Protection Association, said more than one blacklist existed and they weren't fair.
"We became aware of it at the end of last year," Arthur said of tenant blacklists.
"There are a number of landlord Facebook groups where landlords can post anything they like about tenants," she said, indicating the tenant might not know nor would be able to object.
"One has created a list of names, none of which are tenants we know of. But others probably do the same. There is no one single blacklist type central database," she said.
She was reacting to Privacy Commissioner John Edwards saying this week he would focus on the collection, retention and disclosure of information by landlords and property management agencies after his office received a raft of complaints.
Edwards said he was aware of some property management agencies and landlords asking for very detailed information from tenants during selection processes, while others used public forums to compile lists of so-called bad tenants.
Such blacklists lacked transparency and could unfairly keep some tenants out of the market because of inaccuracies, Edwards said.
The NZ Property Investors Federation and Real Estate Institute have condemned the lists.
But Andrew King, former Federation executive director, said he could understand why they were being compiled, given next Thursday's big law change in favour of tenants.
Landlord Peter Lewis questioned the amount of information banks required from investors compared to what landlords could ask about tenants.
"Perhaps we could make the point that if a bank is deciding to lend you $600,000 cash, they are apparently permitted to ask for and analyse your income and spending history in minute detail," Lewis said.
"But if a landlord is going to lend you a $600,000 property they are not permitted to do so. Why are banks allowed greater powers than individuals?" Lewis asked.
Arthur said a number of database websites allowed landlords to upload notices to their tenants but such lists should not become public records.
She cited a landlord giving a tenant notification that they must tidy the garden, for example.
"This is not information that future landlords should have access to, particularly if the tenant resolves the issue immediately," Arthur said.
Australia had a regulated system where landlords lodged certain information but tenants had the opportunity to see that and ask for changes if it was wrong, Arthur said.
"This kind of system has advantages for tenants as it is regulated and can provide the tenant with a database of information that they can use when applying for a tenancy. There is no opportunity for a landlord to include their personal opinion of someone and no unsubstantiated claims," Arthur said.
Renters United spokesperson Robert Whitaker said the lists were deeply worrying.
"Property managers are shortlisting by any mechanism they can. If they have to choose between 20 people, if the name's familiar because they have been seen in this group, they are going to be struck off," Whitaker said.
One property manager said she was a member of a Facebook group for landlords and managers, which listed tenants' details but said she didn't have the time to visit it often.
She raised concerns about tenants who damaged rental properties and indicated it should come as no surprise to that group of people that tabs would be kept on their behaviour and there could be consequences such as a list.
"When you trash someone's property, you don't want to be blacklisted?" the manager said.