"It will just make them feel bad. "
Breastfeeding Authority lactation consultant Dawn Hunter said it should clear up the confusion around the "breast is best" message where women understood breastfeeding was better but assumed formula would cause no harm.
"If it's not human milk, it could ultimately pose a risk to the baby's health.
"Mothers need to know that," she said.
Jan Carey, chief executive of the industry-backed Infant Nutrition Council, slammed warnings as "scaremongering" and said it would create stress and anxiety for parents.
The consultation paper was part of a review of regulation around infant formula composition, labelling and advertising earmarked for 2013. Submissions close next month.