The NSW Environment Defenders office estimates more than 400 landholders could be directly impacted by the proposed Hunter Gas Pipeline route.
The non-government organisation is providing advice to potentially affected landholders after the pipeline proponent Santos was given an authority to survey earlier this month.
The authority means that if the company believes the negotiations with a landholder have broken down, it can appeal to the minister for the right to survey the property.
Santos acquired the Hunter Gas Pipeline in August last year after obtaining renewed licences to explore for petroleum.
If built, the 413 kilometre pipeline would carve through hundreds of kilometres of agricultural and conservation land between the Narrabri gas project and Newcastle. It is estimated about 100 potentially affected landholders live between Muswellbrook and Maitland.
EDO solicitor and head of legal education Jemilah Hallinan said many landholders were concerned about the project's potential impacts on their land.
"There is every reason landholders should be concerned about this pipeline development because it will likely have very significant impacts on land, livelihoods and the environment. HGP Pty Ltd has identified a corridor 200metre wide stretching for hundreds of kilometres and impacting more than 400 landholders," she said.
"EDO is assisting affected landholders along the whole length of the proposed pipeline and helping them to use the law to assert their rights and protect their land and livelihoods.
"Our clients represent a wide range of landholders, from small 'hobby farmers' in the Hunter to the owners of very substantial and highly productive agricultural concerns on the Liverpool Plains."
Hunter Gas Landholder Rights Alliance chairwoman Meg Bowman said the EDO had been of great assistance to landowners who were not experienced in negotiating with large energy companies.
The group's members are maintaining their legal right to deny Santos representatives permission to survey their land.
"We will continue to say no until we are advised by the likes of the EDO that we can't," she said.
People are being very polite. They are accepting the documents offered by Santos and they are asking them to leave their properties because they won't be singing. No one is being angry or aggressive, everyone is polite."
The Department of Planning and Environment said the decision to allow Santos to conduct survey work was made after consultation and a review of landholder submissions for the Hunter Gas Pipeline.
"The Hunter Gas Pipeline is expected to behave in a respectful and responsible manner, and use their rights of access... only as a last resort," a spokesperson said.
Santos has said previously that it will work with landholders to obtain access and compensation agreements before it applied for a pipeline licence.
Local MPs Dave Layzell and Dan Repacholi have urged landowners to speak with Santos.
More than 60 farmers used their vehicles to block Santos trucks from accessing the Wondoba State Conservation Area, south of Gunnedah last weekend.
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