An SEA is an area of significant native plants or wildlife which the council is required to protect under the Resource Management Act.
Iwi assessments are also needed for a range of activities which may have adverse effects on mana whenua values, including air discharges, boring for water and work in coastal marine areas.
Politicians are divided on the iwi consent rule, which Auckland University associate law professor Ken Palmer said must be seen as invalid.
In a letter to the Herald on Friday, Professor Palmer, an expert on the Resource Management Act, said Labour amended the act in 2005 to clarify doubts over consultation, especially with iwi.
"The section unequivocally states 'neither [an applicant nor a council] has a duty under this act to consult any person about the application'."
Council chief planning officer Dr Roger Blakeley disputed Dr Palmer's interpretation, saying a cultural impact assessment was not equivalent to consultation, but similar to a requirement to supply specialist reports, such as from an engineer.
The council, taking into account the cultural impact assessment and other information, made the decision on the resource consent application.
Professor Palmer did not agree with Dr Blakeley's view, saying a specialist report might be justified on matters of land risk, noise and air pollution, etc, but any obligation to consult mana whenua on cultural concerns went beyond this "and impinges on normal rights of freehold ownership".
Labour's amendments to the act to clarify the scope of the assessment of environmental effects "were to address the very practice and judicial controversy over consultation with iwi that Dr Blakeley claims to be justified", said Professor Palmer.
Labour's Maori affairs spokesman, Shane Jones, said the council should assure itself it was taking account of Maori criteria in the act because the average Kiwi would recoil when asked to engage in a long and expensive cultural impact assessment.
Mr Jones said no one doubted the need to embrace obligations to respect sacred sites, but the issue had morphed into something else.
Where consent is needed
*3661 sites of significance and value to mana whenua.
*About 2000 significant ecological areas.
*Adverse effects on issues ranging from air discharges to coastal marine areas.