The eight students, then aged between 13 and 17, sought an injunction in September 2020 to prevent Environment Minister Sussan Ley from finally approving the Vickery coalmine extension project in northeast NSW.

The judgment is due to be handed down on Thursday morning in Melbourne.

The teenagers from four different states are supported by Sister Brigid Arthur, an 86-year-old Catholic nun connected to the Brigidine Asylum Seekers Project.

The class action, prepared by Victorian firm Equity Generation Lawyers, seeks to invoke the minister's common law duty of care to protect younger people against climate change.

The first applicant, Anjali Sharma, 17, from Melbourne, says Australia is facing increasing risk from fires, floods and storms.

"Every consecutive summer is labelled 'the worst summer this country has ever faced', and yet instead of addressing this crisis more mines are being given the green light," she said in a statement.

The Vickery extension project is a proposal to construct an open-cut coalmine and associated on-site infrastructure about 25km north of Gunnedah.

Vickery, which is owned by Whitehaven Coal, was approved by the Independent Planning Commission NSW in August.

The Vickery Extension Project - if approved - will result in 100 million tonnes of carbon emissions over the next 25 years, Equity Generation Lawyers said in a statement.

It has been put on hold for the court case to conclude and still requires the federal minister's final approval.

Australian Associated Press