"This could mean reducing spending for other children in order to spend more on those children in greatest need [and/or] transferring funding from other areas of government activity."
The 72 non-government agencies say the final action plan, due to be published in a white paper on August 31, should be for all children - not just the most vulnerable.
"It is unclear which children are within the 15 per cent - who will be categorised as vulnerable, how is it defined, and who decides?" the groups say.
"There is a high likelihood of false positives and false negatives. This means some children who need extra assistance will miss out and others may be stigmatised unnecessarily."
The groups call for keeping all existing universal and free services for children and tackling wider policies affecting children such as "labour market and welfare policy, adequacy of family income, housing, the strength of community networks and supports, access to transport and communication systems, access to health providers, the justice system".
Unicef NZ advocacy manager Barbara Lambourn declined to specify universal services that might be at risk but examples could include early childhood education, where a 2007 policy of "20 hours free" education for children aged 3 and 4 has already been undermined by funding cuts for qualified teachers and now a funding freeze.
Early Childhood Council chief executive Peter Reynolds, one of the 72 who endorsed the statement, said targeted extra funding for needy children should not be at the expense of quality preschool education for all.
He said preschools were still not allowed to charge fees for children of 3 and 4 for up to 20 hours a week, but they could ask for "donations".
Treasury officials said last year that most parents could and would pay more if they had to.
"That suggests the Government feels it has some wriggle room there to be able to pull back some funding," he said.
"Fortunately the only bad thing in this year's Budget was that there was no annual adjustment based on inflation. It could have been much worse."
Ms Bennett assured the groups that all ideas for the white paper were being "very carefully considered".
"These are complex issues which require some complex solutions."
GREEN PAPER IDEAS
* Vulnerable children's action plan:
* Change spending priorities to help younger children or neediest children.
* Possibly make professionals report suspected abuse.
* Share information about vulnerable children.
* Use schools and preschools as social service hubs.
Agencies' response
* Action plan for all children, including tackling child poverty.
* Don't cut services for other children to fund help for neediest.
* Mandatory reporting may do more harm than good.
* Support sharing information.
* Support preschools and schools as service hubs.
