This electricity line will be laid across the environmentally-sensitive Giritale natural reserve, Minneriya national park and the Sigiriya wildlife sanctuary.
Environmentalists allege an institution tasked with protecting wildlife has acted totally irresponsibly in granting the permission.
They want the transmission line laid in such a manner that the forest reserves are avoided.
Trees would be felled in a 30 metre area along the transmission line for various constructions, including byways, environmentalists point out.
Attempts to contact wildlife director general H.D. Ratnayake for a comment were unsuccessful.