Chocolate producer Cadbury New Zealand says it will use Fairtrade cocoa from West Africa in its dairy milk bars by 2010.
Cadbury says the move to Fairtrade certification was an ethical decision and the result of about two years of negotiation.
Cadbury is already certified in the United Kingdom and is also planning to get accreditation in Australia and Canada.
Though some charities are impressed with the company's ethical stance, farmers are sceptical about the Fairtrade concept.
Cadbury's deal with Fairtrade is the first time a major producer in New Zealand has entered into such an agreement.
Fair trade certification is about helping producers in developing countries become sustainable by ensuring decent minimum prices for their product, enabling them to compete internationally.
It guarantees no no child or slave labour is used when harvesting cocoa beans, which are mostly sourced from Ghana.
Fairtrade says Cadbury's stance will be life-changing for farmers in Ghana who will be able to sell more cocoa which should improve living standards.
But Federated Farmers says farmers in neighbouring countries are likely to be the victims of the deal in that they will no longer get the business.
Cadbury says its decision to use fair trade cocoa in its products will not mean a change in taste or price of a chocolate bar.