"We intend to show that this is the worst Think Big scheme since Muldoon.
"The downstream effects will not be jobs, but an increase in the pollution in our waterways.
"We already are expected to accept a water standard that means rivers are okay for wading and boating and that simply is not good enough."
Mr Woodcock said DFM would be expecting to talk directly with the Ruamahanga Whaitua.
"We do not accept the view held by them that the statistics for Wairarapa are acceptable. One of the myths to bust will be the way those statistics were produced."
Mr Woodcock said when DFM was first formed it was at times called a "'not in my backyard" (NIMBY) group.
"But we have always had a wider interest in what the irrigation scheme would mean for the rivers in our region " he said.
Mr Woodcock said Water Wairarapa and its supporters should be "looking up the road at the Ruataniwha project with its cost blowouts and pull out before more ratepayers and taxpayers' money is wasted on a pipe dream."
Elsewhere the Green Party is calling on the Hawke's Bay Regional Council and its investment arm HBRIC to stop pumping public money into the Ruataniwha Dam.
The call comes on the back of news that it will cost nearly $1 billion to build the dam.
"The Ruataniwha Dam would be an economic and environmental disaster," said spokeswoman Catherine Delahunty.
"Farmers are reluctant to invest in the dam, so why should local ratepayers and taxpayers?
"At present, all funding to build the dam is coming from the public purse, while the benefits of it will go to private users.
"Hawke's Bay Regional Council should call the project off, or risk ending up with a white elephant water scheme that the public foots the bill for," she said.
Ms Delahunty said the scheme would only result in water becoming more polluted.
"Most of the rivers in the Ruataniwha catchment are already polluted and exceed acceptable nitrate levels. Destroying precious rivers to fit more cows and other irrigation-dependent land uses on the land is exactly the wrong way to spend public money."