Papua New Guinea's Mining Minister Byron Chan denies that the deep sea tailings disposal system of the Ramu nickel mine in Madang province is harming the marine environment.
The 1.5 billion US dollar Chinese-run mine has been dumping tailings into the Bismarck Sea since last year after the national court rejected a lengthy legal challenge against it by landowners.
The NGO, Bismarck Ramu Group, says people are already reporting colour changes in the local reefs and sea floor where the tailings are dumped.
Mr Chan says people make assumptions, but lack science to prove, that the deep sea tailings from the mine will effect the marine life.
"After almost a year and a bit, studies have proven that the activity won;t have that effect on the marine environment. we fulfilled the (order which was part of the ) court's decision which was that proper independent studies be done, and the deep sea tailings system is OK."