MANILA • Mining firms in the Philippines have voiced outrage over government plans to cancel nearly one-quarter of the nation's contracts, plus a permit to exploit one of the world's largest known copper deposits.

Environment Secretary Gina Lopez announced on Tuesday that she would cancel 75 of the nation's 311 mining contracts, as well as the environmental compliance certificate of a planned US$5.9 billion (S$8.4 billion) Tampakan copper and gold project.

She reasoned that the 75 mineral production sharing agreements are located in watershed zones and developing them would threaten water supply and quality in those areas.

The Chamber of Mines of the Philippines said it would fight Ms Lopez's decision, warning that it threatened US$22 billion worth of projects. The contracts are for projects in the pipeline but are not yet operating.

"She's out to kill the industry. We do not see a future for us under her," Mr Ronald Recidoro, the chamber's vice-president for legal and policy affairs, said yesterday.

"Her announcement was bloody in all aspects."

Ms Lopez, who was appointed by President Rodrigo Duterte last year, has railed against what she insists are the environmentally destructive and exploitative practices of local and foreign miners.

Mr Duterte yesterday backed her decision - which the industry has said will affect 1.2 million people - saying it was based on law.

"Water is life. If you put at risk the water supply of the community there, you are putting at risk the quality of life of the people," Ms Lopez said on Tuesday.

This month, Ms Lopez also ordered the closure of 23 existing mines and the suspension of five others, saying they illegally encroached on watersheds, leaked waste into rivers and destroyed trees.

The Philippines is the world's top supplier of nickel ore and the main exporter to China, and the Philippine government's actions have impacted global metal prices.

Ms Lopez said mining companies would be given seven days to explain themselves before the cancellation of the contracts would be carried out.

However, the mining industry has warned it will exhaust all legal measures to fight her moves, which are widely expected to be brought before the Supreme Court.

Mining firms accused Ms Lopez of breaching contracts and asked Congress on Tuesday to reject her confirmation as environment secretary.

The Tampakan copper-gold project in southern Philippines had already been stalled by regulation hurdles, including a local government ban on open-pit mining.

Mr Recidoro warned that Tuesday's announcement would be a huge blow for the local economy.

"This will lead to the loss of what will probably be the biggest employer in the area," he said.

AGENCE FRANCE-PRESSE, REUTERS