MELBOURNE • Australia's Environment Minister Sussan Ley approved an expansion of a Whitehaven Coal mine - a decision which comes despite a historic court ruling that she had an obligation to children to consider the harm caused by climate change.

Whitehaven shares climbed on the news, but the eight teenagers who had brought a class action suit against the company's plan to ramp up production at the Vickery mine in New South Wales state said they were shocked and dismayed.

"The emissions from Whitehaven's expanded Vickery coal mine will only make the climate crisis worse and (it) puts our safe future in doubt. The minister should be ashamed of her decision," Bella Burgemeister, 15, said in a joint statement issued by the students yesterday.

Australia, the world's biggest coal exporter, set a world precedent in May when a federal court found that the minister had a moral duty of care to children to consider the impact of climate change when making decisions on new coal mines.

The ruling was seen as creating hurdles for new coal projects and potentially crimping supply.

Mr David Barnden of Equity Generation Lawyers, which argued the case, called Ms Ley's approval "a slap in the face for the global climate change effort".

It was not immediately clear if the students will be pursuing further legal action.

Ms Ley is due to appeal against the court's ruling next month.

Whitehaven, whose shares ended 2.7 per cent higher on the news, said it welcomed the decision.

The open-cut coal mine extension project would double coal production capacity to 10 million tonnes of thermal and metallurgical coal. Ms Ley attached 37 conditions to her approval.

REUTERS