The UN Ocean conference took place in Lisbon in the midst of rising global interest in deep-sea mining but also growing pressure from some environmental groups and governments to either ban it or ensure it only goes ahead if appropriate regulations are in place.

Deep-sea mining uses heavy machinery to suck up off the ocean floor potato-sized rocks or nodules that contain cobalt, manganese, and other rare metals mostly used in batteries.

The International Seabed Authority (ISA), a U.N. body, is drawing up regulations governing seabed mining in the high seas - areas outside any national jurisdiction. Until global rules are in place, seabed mining is not allowed.

Concerned about the potential impacts of deep-sea mining on ocean biodiversity, the Pacific islands of Palau and Fiji launched an "alliance" to call for a moratorium of the nascent industry.

The World Wildlife Fund’s chief Marco Lambertini has warned that the potential impact of mining the deep sea could be “terrifying” and called for strict regulations to avoid yet another environmental disaster.

Emmanuel Macron, the French president, has called for a legal framework to stop deep-sea mining from going ahead and urged countries to put their money into science to better understand and protect the world’s oceans.