An Environment Court judgement against the Otago Regional Council could leave the organisation open to a barrage of legal challenges.
The council has appealed the court's decision to the High Court.
The council's regional policy statement (RPS) became partially operative on January 14.
The document, which all regional councils must create, outlines policies and methods for managing natural and physical resources in the region.
Regional and district plans must give effect to the statement.
Last year the council was trying to finalise its new policy statement, but in the last nine months the Environment Court had asked it to respond to or clarify what it saw as issues with the plan.
In a ruling last month, Judge Jon Jackson said the council had "simply omitted to act" on some of the matters raised.
Therefore it "slightly jumped the gun" on making part of the plan operative earlier this year.
"The purpose of the Act is not achieved by the proposed RPS when read as a whole," Judge Jackson said.
This could weaken the legal standing of the statement.
ORC chief executive Sarah Gardner said the council disagreed with the decision, which if left unaddressed could leave the proposed policy statement vulnerable to future legal challenges.
"We believe an error of law has been made in this judgement, which needs to be addressed as soon as possible.
"This is essential to give everyone operating under the proposed RPS certainty of its legal status, once the RPS is in operation," she said.
One of the several issues Judge Jackson had with the statement was in a policy about outstanding natural landscapes which referred to protecting their "values".
Judge Jackson noted the policy did not protect the landscapes themselves.
Regarding another part of the statement, which the council had attempted to clarify, he said "I do not understand the explanation and I still do not understand the policy".
However, that part of the statement was made operative anyway.
At a council meeting earlier in the week, Cr Gretchen Robertson said the decision could have "major ramifications for all Otago".
"It's important we do go to High Court to sort this out. We do need an RPS."
