Access to infant milk formula should be restricted "more like prescription drugs", a maternity group says.
Hospitals were right to require new mums to sign a consent form if they want their babies fed formula, said Brenda Hinton, a spokeswoman for the Maternity Services Consumer Council.
"In principle I don't have a problem with it. But the policy needs to be actioned sensitively, so women understand why this is happening."
"If a parent is making an informed choice to feed a baby infant milk formula that's their right.
"I do think as a society it would be a good idea if formula was treated more like a prescription drug, something that you use if you are unable to breastfeed."
The Waitemata District Health Board, which runs maternity units at its North Shore and Waitakere hospitals, is among 18 DHBs nationally to require completion of an informed consent document before a baby is fed formula.
The Herald has sought an explanation of Waitemata's policy, but the DHB indicated it was unlikely to respond until tomorrow.
Women's studies academic Professor Maureen Molloy, of Auckland University's department of anthropology, told Fairfax Media that mothers should not have to sign the consent forms to feed their babies formula.
"They seem to be coercive - forcing mothers to sign off on the fact they aren't, in the hospital's view, doing the best thing for their baby."
The Health Ministry recommends exclusive breastfeeding to around six months of age.
"Breast milk is specially made for your baby. It is warm, safe, nutritious and free, which makes it ideal for healthy growth and development and helps protect your baby from illness," the ministry says on a webpage that offers a leaflet on how to safely select and use infant formula.
"It can take some practice for both the mother and the baby before breastfeeding happens easily, but then it can be a very rewarding experience.
"Giving infant formula to a breastfed baby will reduce your milk supply and may make returning to breastfeeding difficult, should you change your mind."
But despite the official "breast is best" message, reinforced through the Baby Friendly Hospital accreditation, Auckland University research has found that most mothers stop exclusive breastfeeding before their baby is six months old.
Isis McKay, the maternal and child health manager of Women's Health Action, disagreed with Hinton's idea of requiring a prescription to get infant formula.
She said providing information about infant formula to parents who wanted to use the products was important, but the objections raised by some women to the informed-consent system indicated it needed to be re-assessed.
"While we understand the importance of supporting women to make informed choices around infant feeding, we do think it is time for a change in how we provide information and support to people who need to or decide to use formula.
"There is so much misunderstanding and misinformation around."