The predator-free target is on top of the 'Battle for Our Birds' aerial 1080 poisoning programme.
The idea of the joint venture is to attract $2 of private sector and local government funding, for every $1 of Government funding.
Ban 1080 Party president Bill Wallace, of Nelson, dismissed it as a pipe dream.
"But it's justification for another 34 years of spreading 1080 in ever-greater quantities," Wallace said.
He doubted private companies would want to be associated with a poisoning programme in which animals died "slow and tortured deaths".
"This is just ludicrous," 1080 activist Laurie Collins, of Buller, said. "They know they haven't got a hope in hell."
Poisoned pellets would have to be laid on the ground anywhere a rat went, including towns, he said.
There were "better things" for the Government to be concerned with when New Zealanders were living in their cars, Collins said.
He also said the West Coast councils could not afford to match the work $2 for $1.
"There's no doubt, over 90 per cent of West Coast ratepayers don't want anything to do with it."
Farmers Against Ten Eighty spokeswoman Mary Molloy, of Hari Hari, said the ideal was laudable but not feasible.
Federated Farmers spokesman for pest management Chris Allen said it fully supported the target, although noting it would take billions of dollars to achieve eradication using current technologies.
"Federated Farmers want an assurance that the money will be made available to investigate new strategies and technologies," Allen said.
New Zealand First said it had the potential to derail into the worst unintentional ecological blunder of modern times.
The party's primary industries and outdoor recreation spokesman Richard Prosser said birds and lizards had coexisted alongside ferrets and stoats for more than 130 years, cats for 200 years, and rats for more than 800.
"The rat is the preferred food of the stoat, which only switches to preying on birds when rat populations are depleted," Prosser said.
The intention of eliminating rats was so unrealistic as to be "bordering on the irrational".
Green Party list MP Kevin Hague said the $28m the Government was initially investing was "a drop in the bucket".
To make Stewart Island predator free would cost up to $25m alone. In addition, DOC's funding had been reduced by some $56m a year on the last Labour government budget, he said.
However, West Coast Regional Council chairman Andrew Robb welcomed the announcement.
He said it would mean a lot more aerial jobs on the Coast, with follow-up ground work, which would also create some employment opportunities.
In terms of the councils putting in $2 for every $1 of private money, he noted a lot of the work would be on Government land.
- Greymouth Star/ additional reporting NZ Herald
