The Government is being called on to set guidelines for preschools on how much exercise children should be having following a new study.
The University of Auckland-led research found 13 percent of early childhood centres surveyed showed children videos or television during the week.
Researcher Sarah Gerritsen says an upcoming review should set clear policy.
"We'd like to see them maybe create some new resources for them -- to encourage active movement in kids -- which they already have, but they definitely could design more for that sector, rather than just for parents in general."
Ms Gerritsen says the study showed only one in three institutions had a written policy on the matter. Those policies were suggestions, rather than requirements, and didn't address limiting screen time.
She says screens stop children from adventuring.
"It takes away opportunities for active play. We know from overseas research that when screens are available, children use them, and they do a lot less moderate to vigorous physical activity."
Ms Gerritsen says the Government should consider enforcing exercise policies in an upcoming review.
The study showed children were engaged in active, teacher-led play for 80 minutes per day, and child-led activity for five hours per day (indoor and outdoor).
They watched television/DVDs daily in 2 percent of services and weekly in 11 percent of services. Children used computers/tablets daily in 11 percent and weekly in 22 percent of services.
Less than half -- 44 percent -- of early childhood education services participated in health promotion programmes with a physical component, with the most common barriers being limited space (10 percent), lack of storage (10 percent) and insufficient funds (9 percent).
The survey included results from 257 early childhood services -- 30 percent of licenced providers in three Auckland regions. The research findings were published today in the Australian and New Zealand Journal of Public Health.