Preschoolers should have limited screen time and more physical activity in early childhood education centres, says a new study.
The University of Auckland survey finds children are watching TV and DVDs at least once a week in 13 per cent of centres - and computers or tablets are used once a week in a third.
But those in the industry say guidelines aren't necessary and teachers can judge what is appropriate use.
PhD student Sarah Gerritsen didn't specify what the optimum screen time should be but international guidelines favour a daily maximum of one hour.
Her research, published today in the Australian and New Zealand Journal of Public Health, also found only one in three centres had a written physical activity policy.
Ms Gerritsen found centres could do more to encourage children to get active.
She surveyed 237 centres in Auckland, Manukau and Waikato and discovered widespread use of digital devices.
This comes as children spend more and more time on devices at home, she told the Herald.
"I'm not saying they should be banned but there needs to be some critical thinking around why we should be using them, and probably some limits on screen use."
Early Childhood Council chief Peter Reynolds said there was a place for digital devices in centres, if use was controlled and appropriately supervised. They should not be used as a babysitter.
And as devices become more widespread, Mr Reynolds said fewer centres were not using them at all.
"The simple reality of it is that pre-school age children of today are going to be highly reliant on their ability to utilise this sort of technology when they hit high school."
Mr Reynolds saw no need for guidelines but was hopeful of some guidance from experts about appropriate use.
"I haven't seen any evidence to suggest there's something definitely broken, for which guidelines are necessary to solve."
That view was echoed by Central Kids Kindergarten chief executive Jan Ballantyne. She said teachers would use their judgment to decide about appropriate screen-time, and often devices were used as an educational tool for learning.
"I don't personally believe that we need to have guidelines. We just have to have more educational material to provide to parents and to teachers from the research about what's ideal. We don't need more bureaucracy."
Suzy O'Connell, of Wellington, has four children aged 3 to 15. The 3-year-old, Lucille, uses digital devices for up to an hour a day at home and at her centre, mostly for educational purposes.
"I think there should be a standard policy," Ms O'Connell said. "I think children only learn by exploration and taking risks physically. What is so important is interaction with other children and life skills."
Sitting at a screen all the time wouldn't deliver that.
Green Party education spokeswoman Catherine Delahunty goes even further, saying digital devices have no place in early childhood education centres. Rather, children should be playing, interacting and being creative.
She said there was no evidence to suggest allowing under-5s to use devices was helpful. "Kids are probably getting screen-time at home. They don't need extra."