The Sustainability Council says a nationwide register of contaminated and potentially toxic sites is well overdue.
The Hawke's Bay Regional Council has been told by Ombudsman David McGee it has no grounds to withhold information about the locations of 1800 potentially toxic sites.
Sustainability Council executive director Simon Terry thinks there could be tens of thousands of potentially contaminated sites throughout New Zealand, yet there is still no national register.
Mr Terry says the secrecy around the severity and locations of contamination is a disgrace.
However, Local Government New Zealand says many of the potentially toxic sites could have no contamination issues and property prices might be compromised if details are publicised.
It says details about the sites are available for people with legitimate reasons.
Environment Minister Nick Smith says he expects every council in the country to follow Hawke's Bay's lead. However, he says the information has be treated carefully.
The Green Party says all contaminated sites should be listed on an open national register - no matter what the impact is on the owners.
Council to obey ruling
Ombudsman David McGee ruled the Hawke's Bay council had no grounds to refuse a request under the Official Information Act.
The regional council identified the sites as possibly contaminated by hazardous substances more than a decade ago, but has not made the list public.
Only some of the property owners know they are on the list.
After a complaint by The Dominion Post, Mr McGee gave the council until 12 October to make the information public.
Council chairperson Alan Dick says the council will obey the ruling, but will write to all 1800 owners of properties on the list next week to warn them first because many will not know their properties are affected.
Mr Dick says the council is trying to find ways to limit the effect on property values.