Details of the deal emerged last week, when the council was asked to start processing the new proposal.
Regional and local planning manager Penny Pirrit told councillors they could vote against it, though they had "limited reasons" to reject it outright.
Te Arai Coastal Lands Trust wants to change a rule in the District Plan to create 44 rural residential lots and two larger titles in return for giving 172ha of reserve land to the council, as well as a 5.6ha wetland.
Te Arai Preservation Society has called for the council to buy the company's 616ha holding outright. The society is backed by a petition signed by 3000 people.
Councillors Cathy Casey, Sandra Coney, Mike Lee and Wayne Walker voted against the council starting the processing of the plan change but they were outnumbered by 13 others, including Mayor Len Brown.
Ms Coney said the Forest & Bird Protection Society believed Rodney's agreement was illegal.
Mr Walker urged the council to gather all its legal power to reject the bid because he had no confidence that, in the processing of the application, the unique environment and threatened fairy tern and New Zealand dotterel would be protected.
Mr Lee said the Rodney Council had made the agreement to let the developer have another go after an independent panel of commissioners had rejected the previous bid.
"I'm not happy with that," he said, noting that the council had broad statutory responsibilities that made it difficult to process the application. "Any development within a kilometre of this breeding site of highly endangered species is irresponsible."
Dr Casey said: "Let's just say no and make moves to buy the land."
Mayor Brown said he could see no grounds for not receiving the application.
He clamped down on councillors' talk of buying the land, saying it would compromise the council's position and push the price up.
A Maori Impact Statement was put before councillors saying the hapu, which owns 25 per cent of the venture, "wished to develop the land in a sustainable manner to better provide for the socio-economic needs of its people".