The United Nations children's fund Unicef says children should have a say when they are adopted and when their parents separate.

The agency's New Zealand branch says adoption and family laws breach the UN Convention on the Rights of the Child, which New Zealand ratified 20 years ago this year.

Advocacy manager Deborah Morris-Travers, who adopted a baby herself eight years ago, said it was impractical to consult babies about being adopted, but it should be compulsory to consult older children.

"With the numbers of children in foster care and the efforts to create 'permanency' and 'home for life', there are a number of children who will find themselves in a situation of potential adoption."


She said adopted children should also have a legal right to find information about their biological parents. Current law allows this only from age 20. "They should be able to access information at the time they start asking questions."

There have been two private member's bills in the past year to reform the Adoption Act, which dates from 1955. Labour MP Jacinda Ardern's bill, which would have required the Law Commission to review the law, was defeated in October. Another bill by Green MP Kevin Hague has not yet been drawn from the parliamentary ballot.

A Unicef report published today also criticises family law changes that require lawyers for children to ensure the child's views on a parental separation are put in court, but no longer require the lawyer to act in accordance with those views. The lawyer must now act "in a way that the lawyer considers promotes the child's welfare and best interests".

The report also proposes raising the age at which children leave the care of the Child, Youth and Family Service from 17 to 18, in line with the UN's definition of children.

Justice Minister Judith Collins said she had no immediate plans to amend adoption legislation.