Te Rūnanga o Te Rarawa is blaming the Far North District Council and the Northland Regional Council for the pollution of the Wairoa Stream in Ahipara.
The stream is a popular swimming spot for locals and a food source for the iwi.
“Flounder, mullet, whitebait, eels, herring and so much more can be found here," said Roma marae chairman, Hone Paetai.
"But now, we are afraid to eat food from here because the water is contaminated. Our children are warned not to swim here.”
The rūnanga commissioned Streamline Environment and Wai Kōkopu Consultants to carry out tests on the quality of the water.
Their report confirmed the presence of faecal coliforms in the Wairoa Stream, due to the overflow of domestic sewage or non-point sources of human and animal waste.
Harmful levels of metals such as arsenic, cadmium, chromium, copper, lead, and zinc were also found.
The report stated consent conditions for the Ahipara wastewater treatment plant and landfill had not been been met on several occasions. Monitoring procedures and practices by both councils had also been lax.
"The report has confirmed our fears and increased anxiety for the ongoing utilisation of the river by our community,” said Haami Piripi, the chair of Te Rūnanga o Te Rarawa.
The Northland Regional Council has agreed to meet iwi and kaitiaki representatives on-site to discuss concerns.
The Far North District Council did not respond to requests for comment.