Photos of the old mercury mine at Puhipuhi show it in a dangerous condition.
Spokesperson for the Puhipuhi Mining Action Group, Jenny Kirk, says PMAG and Ngati Hau want it cleaned up.
"We also want to know if the extremely high mercury water and sediment levels at the test spot near the old mine indicate that the old mine is leaking toxic wastes into local waterways," she says.
In a letter sent to the Northland Regional Council, with photos, Ms Kirk says "just as worrying is the effect of those high sediment levels should there be a huge storm event in the area, and movement of the toxic sediments further into the waterways and eventually down to the Kaipara Harbour"
When mercury is dumped or leached into waterways, high concentrations of mercury can accumulate in fish (and other animals) posing a danger to people and the environment, she says.
"Ngati Hau, and ourselves, have been complaining about this, and questioning the NRC for years - so far to no avail," Ms Kirk says.
"Isn't it about time, the NRC took its environmental responsibilities seriously and started work to remediate the old mercury mine ?"