Children's advocate Dame Lesley Max wants more promotion of contraception as a step towards tackling child abuse.
She told a public meeting in Mt Roskill yesterday about a man who came to a parenting class in Papakura saying his goal in life was to have 11 children - even though all his children so far had been taken off him by Child, Youth and Family.
"He doesn't care for them. He can't care for them. He enters relationships with one vulnerable woman after another, and our system enables him to do so."
At last count the man had exceeded his target, fathering at least 12 children with at least three women. Dame Lesley said he was not working. She thought all his ex-partners were on the domestic purposes benefit.
"So I say let's use our best efforts to slow down the pipeline of the production of vulnerable children. Let us very actively promote and facilitate family planning."
Social Development Minister Paula Bennett, who called the meeting to debate her Green Paper for Vulnerable Children, did not comment.
But a working group which reported last year on proposed welfare reforms recommended providing all parents on welfare with "ready access to free long-acting reversible contraception".
A Families Commission report this week noted "a link between maltreatment and large families, multiple births or children close in age".
"There may be scope for targeting family planning education to parents who have had previous children removed," it said.
Long-acting Jadelle implants, small removable rods inserted in the arm, have been fully funded by Pharmac since 2010 and last up to five years. But Labour social development spokeswoman Jacinda Ardern, who was also at the meeting, had heard they were not always available.
Dame Lesley, who brought the Home Interaction Programme for Parents and Youngsters (Hippy) to New Zealand in 1992, said the most vulnerable families often did not even think about contraception.
"My experience, after 20 years of being responsible for a community agency with families facing multiple challenges, is that the planning of families is something that is hardly considered, hardly talked about, and children just happen without intent."
She said government programmes such as Strengthening Families, which co-ordinates agencies working with a family on multiple issues, ignored family planning.
"There has been a sense that maybe it's too personal. But I think it can be handled with sensitivity."