The Canterbury Medical Officer of Health is warning some of the region's drinking water could cause a potentially fatal disease in newborn babies.
Alistair Humphrey says nitrate levels in the Canterbury region are climbing due to intensive farming and have reached dangerous levels in a number of areas.
Dr Humphrey says many private and small water bores in the Ashburton area have dangerously high nitrate levels and that is particularly risky for bottle-fed newborns.
He says an infant who is bottle-fed that water could end up with blue-baby syndrome, which can be fatal. There has been one confirmed case of the syndrome in New Zealand, but he believes there may have been more that were misdiagnosed.
The Canterbury water management strategy needs to make reducing the nitrate levels a priority, Dr Humphrey says.
The district health board is advising midwives and GPs to warn parents of the risk.
A midwife with the Canterbury Breastfeeding Advocacy Service says parents in the region need to be cautious.
Carol Bartle says people should buy a liquid ready-to-go formula or mix powdered infant formula with bottled water. Nitrate is not transferred through breast milk.
However, farmers say it is unfair and alarmist to blame them for the high nitrate levels in the region's drinking water.
Federated Farmers says the levels are worrying, but mid-Canterbury provincial president Chris Allen says it is important not to jump to conclusions until more research is done.
Mr Allen says it is possible that agriculture is having no effect and the levels might improve naturally over the next few years and is calling on the Canterbury regional council to investigate the matter.