The World Wildlife Fund in New Caledonia says a burst effluent pipe at Vale's nickel plant is just one example of its faulty equipment causing environmental damage to the area.
Vale suspended operations in mid-November after it became known that the pipe, leading through a lagoon of a World Heritage Site, was broken.
The WWF New Caledonia manager, Hubert Geraux, says the burst pipe shows Vale is incapable of preventing major faults.
He says other equipment owned by Vale is not up to standard, including residue storage basins which are leaking and above the authorised upper safety limit.
He says lethal concentrations of sulphur dioxide are destroying the forest around the works site, and silt and acid leaks are affecting streams in North Bay and West Kue.
Mr Geraux is also calling on the role of Environment New Caledonia, or L'OEIL, to more actively assess the impact Vale might be having on the region.