Some landlords were reluctant to invest in their properties and many did not know their legal obligations.
He called for mandatory registration of landlords as well as regular assessments for all rental homes.
"I am for a building warrant of fitness, but it does have to include regulators out in the field making sure landlords are meeting a set of criteria."
The trial was conducted by a steering group, which included the University of Otago Wellington, the Green Building Council, the councils of the five cities in which homes were tested and the Accident Compensation Corporation.
It looked at weathertightness, insulation and ventilation, lighting, heating, condition of appliances and building safety.
Property Investors Federation executive officer Andrew King said while some landlords could do better, most were adhering to the Residential Tenancy Act providing safe, sanitary and clean properties.
He acknowledged that many properties failed the test, but "most of those were on small things".
Trial organisers said that although 94 per cent of the inspected homes failed, 36 per cent would require only minor fixes costing between $50 and $150 to pass.