The Royal Forest & Bird Society is sounding alarms over a request by Far North Mayor Wayne Brown to explore more territory for minerals.
The mayor's exploration company, Tai Tokerau Minerals, was granted permits in July to prospect for gold and silver on land between Kaeo and Whangaroa.
But the Government's Petroleum and Minerals website shows the company has since applied to extend the permits in two areas.
Northland Forest & Bird president Dean Baigent-Mercer says that is a concern because it takes any potential mining closer to communities like Kaeo, Matangirau and Matauri Bay.
He says Kaeo is flood-prone and would be at risk of pollution, if mining were to go ahead in the surrounding hills.
Mr Brown says his company has applied for permit extensions because the Government's draughtspeople had drawn arbitrary lines through the geological features of most interest.
He says extending permits for that reason is common practice, and exploration poses no risk to the environment.
The mayor is a strong advocate of mineral exploration in the north, because of the economic benefits he says mining can bring.
He has previously said that he set up an exploration company to show his confidence in the region and put his money where his mouth is.