NSW Premier Bob Carr says any legal challenge over the approval of the charcoal plant near Mogo, south of Batemans Bay in the state's south-east, would be lost.

Environment groups have indicated they will mount a legal challenge in the Land and Environment Court over the State Government's approval of the plant.

Mr Carr says he has heard so many untruths over the development.

"No trees are going to be cut down and used in this development, this development is going into a quarry, it cannot be...[seen] from the highway," he said.