THE Nationals have defended voting against a Greens Bill that aims to give farmers protection over mining.

The move comes as opposition to coal-seam gas mining in Colac grows and independent MP Tony Windsor introduces legislation to allow the Federal Government to ban mining where it could hurt aquifers.

The Greens' Landholders Right to Refuse (Coal Seam Gas) Bill would have allowed farmers to bar mining companies from entering their properties, but the Government and Coalition voted it down.

They had blocked a Green bid for a moratorium on coal-seam gas the previous week.

Greens environment spokeswoman Larissa Waters said "the old parties" had "spoken at length about their intention to deny farmers any rights to protect their prime agricultural land from coal-seam gas".

"Both Labor and the Coalition are allowing the mining industry to continue to ride rough-shod over Australian farmers," Senator Waters said.

But Nationals Senate leader Barnaby Joyce dismissed the criticism.

"We take the issue seriously, (but) this is a Greens political tactic," Senator Joyce said.

"The National Party brought about the extension of terms in the senate inquiry into CSG, that will finish mid-November.

"Then we'll have greater capacity to get the numbers to bring some form of change."

Senator Joyce said there "has to be re-establishment of greater rights to farmers".

Aquifers and prime agricultural land needed to be protected and returns to farmers needed to be greater where there was mining, he said.

Meanwhile, Colac Otway shire has written to miner ECI International asking it to end its search for CSG in the area.

ECI has a permit that allows it to conduct exploratory drilling over 500sq km, including Forrest, Gellibrand and Colac.

Colac mayor Brian Cook said ECI would have to "fight the community all the way".