A Supreme Court challenge has been lodged against the Environmental Protection Authority's approval of the LNG hub, north of Broome.

The Wilderness Society has joined forces with traditional owner, Richard Hunter, to allege that the decision making process breached the Environmental Protection Act.

Earlier this year the EPA Chairman Paul Vogel was forced to assess and ultimately approve the project on his own, because the other four board members had conflicts of interest.

The Society's Heidi Nore has told AM the legal action will allege that three of the board members still had some input.

"We had a situation where there were three conflicted board members deliberating for three years, discussing the matter, privy to confidential information, shown around the site by traditional owners, shaping the way the discussions were for three years before finally stepping down because of their conflicts of interest."

Neither the EPA, nor the Environment Minister, Bill Marmion, were available for comment.