Upper House Greens MP Lee Rhiannon told a meeting of more than 100 people that laws covering gas and oil searches "lock out" the community and individual property owners.

"One way we can have an impact is when your voice, the public voice, is strong . . . ," she said.

Residents should not rule out civil disobedience such as the recent farmer blockades used against BHP Billiton on the Liverpool Plains, she said.

The Department of Primary Industries has approved Sydney Gas and AGL exploration for coal seam methane gas in the Lower Hunter.

Outside the meeting, Sydney Gas general manager Mark Harper told The Herald people were "confused" about the activities.

The companies are conducting exploration drilling between Broke and Wollombi and there are plans for more sites throughout the area.

Residents claim exploration and possible future production threaten underground water and the scenic beauty of the Wollombi Valley.

"The objective [of the residents] is to get us out of here by any means," Mr Harper said.

Cessnock councillor James Ryan told the meeting that Sydney Gas' exploration licences received a minimum of environmental assessment.

If the company proceeded beyond exploration, the development would be subject to Part 3 A provisions, which left approvals in the hands of Planning Minister Frank Sartor.

He said the Wollombi Brook was considered by the Hunter-Central Rivers Catchment Management Authority to be a highly stressed river and climate change could extend its existing no-flow periods.

Mr Harper said the visual impact of gas was less than large coalmines such as those near Broke and if people cared about climate change they should support gas.

"I would be fighting coalmines," he said.

The meeting was held in Laguna, south of Wollombi.