Cameron said many mothers couldn't breastfeed for many reasons and they shouldn't be punished for it.
A Canterbury District Health Board spokesman said this was standard practice in many parts of New Zealand.
There was a duty of care to provide food for breastfeeding mothers as they are patients' main food source - and other parents could pay $5 to receive a meal too, he said.
Christchurch Hospital's policy is to provide breakfast and tea or coffee free for parents, and free meals on the ward for breastfeeding mothers if the baby is under 6 months old, according to the Canterbury DHB website.
Additional food and drinks can be purchased from the Christchurch Hospital facilities or vending machines. Hospital meals can be ordered and provided at $5 for parents who are unable to leave their child, the website says.