Plans for a major coal mine expansion failed to consider broad environmental impacts, the High Court found.

In a landmark decision on Wednesday, the High Court ruled against the proposed expansion of the Mount Pleasant coal mine near Muswellbrook, in the Upper Hunter region of NSW.

It is the first time a court has upheld that project approvals must account for the broad environmental impacts of burning fossil fuels.

Environmental campaigners have termed the decision a victory for all Australians and called on the government to move away from fossil fuels.