Unregulated mining in the deep sea should not be allowed to go ahead, the head of the United Nations has warned.

“The deep sea cannot become the Wild West,” UN Secretary General António Guterres said at the opening of the UN Oceans Conference in Nice, France.

His words were echoed by French President Emmanuel Macron, who declared the “oceans are not for sale”.

The remarks appear to refer to the decision by President Trump in April to begin issuing permits for the extraction of critical minerals in international waters.

There is increasing interest in extracting precious minerals from what are called metallic “nodules” that naturally occur on the seabed.

But marine scientists are concerned about the harm that could be caused.

“The ocean is not for sale. We’re talking about a common shared good,” President Macron said. “I think it’s madness to launch predatory economic action that will disrupt the deep seabed, disrupt biodiversity, destroy it.”

This issue is one of a number on the agenda in France, including over-fishing, plastic pollution and climate change.

Over 2,000 of the world’s scientists met last week to review the latest data on ocean health – they recommended to governments meeting this week that deep sea exploration be halted whilst further research be carried out on the impacts.

More than 30 countries support this position and are calling for a moratorium – but President Trump has not rowed back on his executive order.

A key aim of the UN oceans conference, which runs until Friday, is to get 60 countries to ratify a High Seas Treaty and thus bring it into force.

This agreement was made two years ago to put 30% of international waters into marine protected areas (MPAs) by 2030, in the hope it would preserve and help ecosystems recover.

President Macron declared in his opening speech that an additional 15 had ratified but that only brings the total number to 47.

The UK government has not yet ratified the agreement, though on Monday it said a ban on a bottom “destructive” type of fishing that drags large nets along the seafloor could be extended across MPAs in England.

Even if enough countries sign there are concerns from environmentalists, including Sir David Attenborough, that there is nothing explicit in the Treaty to ban bottom trawling in these MPAs.

Bottom trawling is one of the more destructive fishing practices that can lead to accidentally killing larger marine species.