Lewis Road Creamery has repackaged its most popular milk for charity, but the "breast milk" has been slammed as "unacceptable" by breast feeding advocates.

For three months the blue top organic homogenised cow's milk will be slapped with the red label reading: "Breast Milk: the cow's milk that funds the cure".

The collaboration with Breast Cancer Cure was pitched to the popular dairy producer and will be on New Zealand shelves from today. Twenty cents from each bottle will be donated to the charity, committed to finding a cure for breast cancer by 2018.

However, New Zealand Breastfeeding Authority chief executive Julie Stufkens said the move was disrespectful towards women.

"Sadly I think this is misguided advertising," she told stuff.co.nz.

"Labelling a cow's milk product as breast milk is not acceptable.

"The product does not contain any human milk and does not come from a breast but an udder."

Stufkens said she was concerned mothers could mistake the product as breast milk.

However, Le Leche League New NZ spokeswoman, Lisa Manning, disagreed, saying she didn't think people were that "silly".