The company rejects these claims, saying it will refill and replant the open pit once the ore has been extracted, and that all necessary care is being taken not to pollute the environment.
Earlier this month the Environment Agency granted an environmental permit stating it would not "significantly" pollute the environment or harm human health.
Some of the proposed the legislation around carbon pricing proceeds from the idea that companies do not pay the full cost of consuming valuable natural resources that also pollute the environment, and instead pass substantial costs to taxpayers.