"The spills from the Hillgrove mine stand as a clear warning not to allow a new open cut antimony mine at Wild Cattle Creek," Mr Buckingham said.

"The Wild Cattle Creek area received 185mm of rain in the past week. To allow mining of toxic metals at the top of the Nymboida-Clarence catchment would be negligent and puts at risk the health of the Clarence River and the purity of Coffs Harbour's drinking supply.

"The Greens are not against mining antimony, but the top of a catchment with such steep terrain and high rainfall is simply the wrong place."

Coffs Harbour Greens councillor Mark Graham said that mining had already necessitated building a special facility to provide clean water for the village of Bellbrook (west of Kempsey). Bellbrook, which sources its water from Macleay River bores, opened a new water supply plant in June after issues with water quality forced Kempsey Council to cart water to the village.

"Bellbrook's water supply was contaminated with arsenic and antimony and $1 million was invested to provide a safe water supply for the village," Cr Graham said, adding that if the current plans for the Wild Cattle Creek mine go ahead, pollution of the Coffs Harbour water supply was "inevitable".

"We have the highest rainfall catchment in the state. If mining goes ahead at the top of the Nymboida-Clarence catchment, it is guaranteed that the Coffs Harbour water supply will become contaminated."

"If that happens, we will be looking at a minimum of $40 million to build the facilities required to remove the contamination."