Former Fonterra Shareholders Council chairman Simon Couper says the Trading Among Farmers (TAF) model is unable to deliver 100% farmer ownership and control.
Couper, who resigned yesterday, says it has always been a strong principle of his that the ownership and control of the co-op must be protected.
"TAF theoretically provides a unique opportunity for our co-op but absolutely must have complete safeguards around ownership and control"
While the board and council have made some progress he was convinced there were factors that needed to be in place to protect the co-op, he says.
"Fund size was key in my decision and a threshold of anything over 15% puts the co-op at risk"
He says farmers must realise TAF "will put us on a path that has the potential to become a slippery slope".
"I've always held to my integrity. I accept that a majority of council maybe happy with the proposed model but I couldn't lead an organisation where I had such a big fundamental difference on such a big issue"