Landlords should be licensed to drive law-breakers from the industry, the Property Managers Institute says.
Chairwoman Karen Withers called for a licensing scheme amid revelations one Auckland landlord can still have tenants - despite being fined almost $180,000 for breaking tenancy laws.
While most landlords did the right thing, it was worrying that Widhani Iskandar had continually flouted the law, Withers said.
"A licence could mean landlords ... get a little tick beside their name or a number to prove to potential tenants that they are doing it all properly and everyone knows they are working to the same standards."
Iskandar - who goes by the name Debbie and managed up to 100 rental properties in South Auckland - "deliberately and knowingly" failed to lodge her tenant's bond payments in 81 cases.
She was last week ordered to correctly lodge $119,625 in bond money and pay $10,495 in costs after 197 complaints were brought against her at the Tenancy Tribunal.
Iskandar was further ordered to pay $700 to each of 68 tenants, whose bonds she had handled illegally.
Her latest transgressions come after she illegally rented out converted garages for well-above market rent in 2016, during the peak of the housing crisis.
Debate about renters' rights has come into sharper focus with home ownership levels at their lowest in 60 years and more Kiwis facing the prospect of long-term renting.
Tenants currently deal directly with private landlords - who personally manage the rental properties they own - in about two-thirds of cases, the Property Investors Foundation said.
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The remaining rentals are usually managed by property managers, who deal with tenants on behalf of the property owner for a fee.
There are no requirements for either landlords or property managers to be licenced or accredited.
Last year there were loud calls for property managers to be regulated after stories emerged of them charging fees to process applications faster and asking to see tenants' bank statements so they could judge their spending habits.
Withers supports calls for property managers to be licenced and said regulations for private landlords could be introduced at the same time.
Private landlords without a licence would be barred from managing their own properties and forced to outsource the job.
This would ensure tenants experienced a consistent level of service and protect them from the likes of Iskandar.
The Ministry of Business, Innovation and Employment, which took Iskander to the Tenancy Tribunal, said there was currently "no legal provision for us to exclude someone from being a landlord".
Housing Minister Phil Twyford said the Government had been examining ways to enforce rules around tenancies, including looking at penalties for bad landlords, and would be making "announcements in the future".
Green Party building and construction spokesman Gareth Hughes was adamant Iskandar's case showed stronger laws were needed.
It was appalling she had been able to continue operating as a landlord after such "a gross breach" of her legal obligations, Hughes said.
Withers said licensing for landlords should be far easier than for property managers and pointed to a system in Wales where landlords completed simple online tests to prove they understood tenancy laws.
Property Investors Foundation president Andrew King had looked at the Welsh test and agreed it was simple. But he didn't want mandatory licensing for landlords.
His foundation regularly ran education sessions for members and would prefer new measures that encouraged landlords to attend similar courses.
Real Estate Institute chief executive Bindi Norwell said her team had been calling for property managers to be regulated for more than 10 years
"While regulating landlords is a good proposal to support tenants, it's our belief that we need to start with property managers first and then look at extending the regulation to landlords," she said.
South Island property owner Angela Strang, the Property Investment Federation's 2015 landlord of the year, didn't want mandatory licencing either.
She would support a free Government-run online quiz that could be completed by landlords and tenants, then printed out to show each other they understood tenancy laws and knew how to behave respectfully.