Greenpeace warns sea-bed mining could have a huge negative environmental impact.
A Canadian mining company, Nautilus Minerals, has made sea bed test extractions in PNG and is starting explorations in Tonga.
It has also lodged exploration licence applications in Fiji, Solomon Islands and New Zealand.
The company says a yet to be published scientific impact study found sea-bed mining is environmentlly safe.
But Greenpeace's Pacific Oceans team leader, Nilesh Goundar, says too little is known about the effects of deep sea mining.
"The mining and dredging process destroys the ocean floor and can have severe detrimental impacts, impacting both species and habitats. And it may also interfere with ecosystem processes and have consequences for other activities, such as fishing, by destroying important fish habitats. So we would really call for caution."
Nilesh Goundar says more than one independent scientific study should be done before sea bed mining is allowed.
