Some of the strongest opponents to coal mine developments have agreed to work with mining giant BHP Billiton on exploration assessments.

Landholders on the Liverpool Plains, in north-west New South Wales had locked their gates in ardent resistance to BHP’s plans for a coal seam gas program in the valley, but will now help prepare one of the assessments needed for approval.

A deal has been struck for the farmers and miners to work together on the Agricultural Impact Statement (AIS), which is used to examine the risks to agriculture and find measures to limit negative impacts.

But the politician who set up the rule that CSG projects near significant water resources need extra approvals, known as the ‘water trigger’ law, says the agreement is a trap.

“I think it's certainly a major step in the right direction,” said local farmer Tim Duddy, one of the people spearheading the campaign against BHP's Caroona Coal Project.

“I am optimistic that hopefully as these things come up we can change these processes so that they do properly assess these agricultural resources,” he said.

Under a recent New South Wales Government measure, the most valuable and productive agricultural areas are deemed ‘Strategic Agricultural Land’, and require more stringent measures from mining companies to prove they will not be affected.

Mr Duddy told the ABC that having landowner involvement in this process is vital.

“We believe we need to show the process for what it is and the only way to do that is to participate in it,” he said.

“So that when we get to a point where things still haven't been assessed at the end that the government comes to the realisation that the process is not sufficient to deal with these projects.”

Former president of the National Farmers' Federation Jock Laurie will act as a mediator between the farmers and miners.

“When you thrust two industries into each other's backyard and just expect them to get on there's antagonism right from the word go,” Mr Laurie said.

“Obviously that antagonism has been going now in this area for about five or six years.

“The company and the farmers and the communities have never really got on particularly well, they don't trust each other and we needed to find a way to break it down,” he said.

Independent Member for New England Tony Windsor, the creator of the ‘water trigger’ rules, says the farmers have been duped.

“I think it's a sand trap for the farmers - [they] enter into a negotiation process and I bet the minister and others say this is step forward,” he said.

“[They] enter into this process, which takes them down a pathway that they won't be able to step back from.

“The integrity of the region is what's in play, not the integrity of individual blocks of land or 2000 acres that BHP may want to mine.

“It's the water that's the key here, not the land.”