An environmental group claiming a lease was granted to a mining company to thwart protests near a contentious proposed waste dam in Tasmania say they were denied fairness in court.
Chinese-owned mining company MMG was in 2022 granted a lease for an 8km access road to the planned dam at the mine near Rosebery on the state's west coast.
The Bob Brown Foundation, which has campaigned against the dam project, has argued the lease was granted to prevent protesters and media accessing the site.
The foundation in April lost its Supreme Court application to have the lease, granted by the state government, reviewed.
However, it appealed against the decision on four grounds, with the matter heard before the full bench of the Supreme Court of Tasmania on Monday.
The foundation says the decision failed to properly consider the lease was granted for an "improper purpose", mainly to thwart, restrict or constrain protest activity near the road.
The foundation also argues it was denied procedural fairness by a court ruling that prevented it from cross examining then-state resources minister Guy Barnett, and his rationale for granting the lease, in court.
Barrister Chris Gunson SC, representing the foundation, described the proposed dam as a highly contentious issue and a matter of public interest.
Mr Gunson said MMG didn't need the lease because it already had access to the road.
Lawyer for MMG, Michael O'Farrell SC, said there was no reason to draw an inference the minister was intent on thwarting protests.
The lease was necessary so MMG could widen and improve the road to give machinery better access, he said.
The three-judge appeal panel will hand down their decision at a later date.
The call on whether to approve the dam is in the hands of federal Environment Minister Tanya Plibersek.
MMG has previously said it needs a new tailings dam for the mine to operate past 2024 and the proposed site is the company's preferred spot.
The dam was given the green light by the Scott Morrison government several years ago but the approval was declared invalid by the Federal Court.