UPDATE: AGL has urged farmers blockading a NSW dairy farm to allow its workers to do their jobs safely.

Farmers started gathering at the farm, outside Gloucester, north of Newcastle, yesterday afternoon after the coal seam gas company began bringing equipment onto the property.

About 20 farmers have gathered there this morning in protest.

The company has permission from the farmer to begin exploration on the property but farmers on surrounding land want seismic and water studies done first.

"It's not up to individual people to let them on because it's everybody's water that is threatened by it," said Drew Hutton of Lock The Gate, a farmers' protest group.

An AGL spokeswoman today said the company respected the right of people to protest and it would continue to talk to the community about its gas exploration activities.

"In the meantime, we urge protesters to also respect our right to go about our activities in an orderly and most importantly, a safe manner," the spokeswoman said in a statement.

Lock The Gate said AGL is licensed for 110 wells in the Gloucester Valley, but the company said the current drilling program is about gas exploration and not linked to the gas production wells.

"We hold approvals for this exploration program to be conducted on private land and have landowner access agreements in place," the spokeswoman said.

"We'd like the community to know that we already have a comprehensive groundwater monitoring network in place with about 25 bores that have been gathering data for the last 12 months."

She said seismic surveys had been used to site the bores.

NSW Greens MP Jeremy Buckingham congratulated the local community.

"The government has refused to listen to the community's calls for a moratorium on coal seam gas, so Gloucester has launched its own moratorium by blockading access to the planned drill sites," he said in a statement.