Fonterra says it will not stop using permeate in its fresh milk, despite a debate raging on the other side of the Tasman.

Milk permeate, a natural waste product from the ultra-filtration of milk, is banned in parts of the world.

Fonterra adds it to blue milks to ensure the protein composition is consistent. A spokesman said that was done to keep the milk in line with the country's food standards, which state that milk must contain 3 per cent protein. The amount of permeate included was commercially sensitive, he said. However, in Australia it is up to 16 per cent of the final product and consumers are being told by other producers that it is effectively being used as a filler.

"Variation in protein composition occurs because New Zealand milk production follows the lactation and feed cycle of cows. Because protein levels are higher during the autumn and winter seasons, more permeate is added," the Fonterra spokesman said. Food laws ban milk processors in Britain and the United States from putting permeate in fresh milk.

The Fonterra spokesman would not comment on that.

"Our focus is here in NZ and ensuring consumers have a consistent product to enjoy all through the year."

Sales of boutique brands leapt 45 per cent since consumer fears about permeate additives spiked in Australia in April. Small Kiwi-owned A2 brand milk, promoted for its health benefits, has 5.5 per cent of the Australian market, up from 3.5 per cent last year. Goodman Fielder also adds permeate to milk.

Here, Graeme Brown, of Canterbury firm Klondyke Fresh, said his firm, Fresha Valley and Green Valley, do not add permeate. "Our point of difference is that we don't add anything, it's as the cow intended."

Brown said the additives debate had not been taken up at the same rate here. Whether supermarkets followed Australia was up to consumers, said Luke Schepen of Progressive Enterprises. "You have to listen to what customers want."