Councils are going to be told not to build or approve developments or structures lower than 1.9 metres above the high tide mark under new advice on rising sea levels.
It's a half-metre increase on the Ministry for the Environment's previous advice a decade ago, based on new information showing sea levels will rise faster than anticipated.
The detail - and other new guidance for councils - emerged in a briefing document provided to a regional council and gives an insight into the Ministry's delayed official guidance to local government which was meant to be published last year.
It also refers to "retreat" as a planning option for areas facing an encroaching ocean - a step that would see land surrendered to the tide and communities potentially relocated.
The guidance to councils is important as local government is being lined up to carry the load for preparing their own areas to deal with the consequence of the sea level rising.
The notes accompanying the briefing stated: "Central government has largely left it to local councils to manage the effects of climate change, but has focused on providing information and some national direction."
A spokeswoman for the Ministry for the Environment said the report was a draft and not yet ready for release, with no decision yet made on when it would be made public.
The briefing document bullet-points weaknesses in the current approach, with local councils said to be seeking "central government leadership and support" and "community understanding and buy-in on the need to act on climate change impacts now".
Thames-Coromandel District mayor Sandra Goudie burst out laughing when she was read that section.
"How many communities are going to want to put their hands up? They can spin out all the gobbledygook they like. What do they want us to do?
"They keep talking about the challenges. Where's the money, honey? If they want us to do something particular like relocating, they better come up with the dough."
The Waikato town of Thames is known to be vulnerable, with much of the low-lying parts of the town likely to be submerged on sea-level projections.
"We've got quite a few people living on the flat around Thames," said Goudie. "Do you want to come into town and say 'we think you're going to be flooded - we want you to pick up sticks and move to a house on the hill. And by the way, we're going to rate you (increase rates to pay) for it'."
"They are tossing council into the money pit every chance they get."
Goudie was planning on reading the latest advice next week but said her response kept coming back to: "What do you want us to do, and where is the money to do it?"
Thames lawyer Denis Tegg stumbled across the document and blogged on it, saying the sea level rises used by the Ministry for the Environment were conservative against latest estimates.
He said councils need to begin incorporating sea level changes with current development plans, raise floor levels and prepare for "managed retreat".
He said the New Zealand Coastal Policy Statement required councils to identify coastal hazards against a backdrop of sea levels rising and climate change over a 100-year span, then include that information into district and regional plans.
"Some councils - such as for example Hawke's Bay - are on the job, have engaged consultants, done all the site-specific mapping and are now well into community engagement.
"In contrast the Thames-Coromandel District Council and the Waikato Regional Council have yet to tackle coastal flooding hazard which threatens whole towns."
Green Party MP and environment spokeswoman Eugenie Sage highlighted the section in the notes in the briefing about central government landing the response on local government.
"That's a failure of leadership. We need a partnership between central and local government.
"Communities like Thames, Kapiti Coast and South Dunedin can't be left to cope on their own.
The government is failing to provide the leadership and support that local councils and communities need in responding to sea level rise."
She said there had been "endless delays and secrecy" around the updating of the ministry's guidance to local government.
"We shouldn't have to rely on the sharp eyes of people like Denis Tegg to find an MFE staffer's PowerPoint presentation on the Waikato Regional Council website. It's certainly more informative than anything Ministers have been prepared to release to date."
Victoria University's Professor James Renwick, who specialises in climate science, said the update was overdue and was needed. He said the briefing document appeared to be using outdated figures for sea level rises.
"Basically, we have to retreat from the coast. Water is coming inland."