The acting head judge of the Family Court has called for gay and lesbian couples to be given rights to adopt children, just as a private member's bill on the issue goes into the ballot for Parliament's order paper today.

Paul von Dadelszen says New Zealand is lagging behind many other countries and should allow both homosexual couples and de facto heterosexual couples to adopt children.

A bill proposing this, sponsored in the last Parliament by Green Party co-leader Metiria Turei and now taken up by gay Green MP Kevin Hague, is in a queue of 30 private member's bills that will go into a ballot today to choose the next members' bills on the parliamentary order paper.

Former Labour Government Justice Minister Annette King said the issue was "on our work agenda" before the election but she ran out of time before losing office.

But the National Government's Justice Minister Simon Power said the issue was not on his work programme.

Judge von Dadelszen, who usually sits in Hawkes Bay, is acting head of the Family Court while Principal Judge Peter Boshier is overseas until next month. He said his speech to a seminar in Wellington on Monday was in his personal capacity and did not represent the court's collective view.

He said the Adoption Act, which has not been fully reviewed since 1955, was outdated and unjustly discriminatory, breaching the Bill of Rights Act, the Human Rights Act and the United Nations Convention on the Rights of the Child.

Only married couples and individuals can adopt children under the act. Lesley Belcham of OUTLine NZ, formerly Auckland Gay Lesbian Welfare, said the issue had been an emotional one for many years.

"If one partner can adopt but a couple can't, the imbalances and inequities of that within a relationship actually cause a lot of pain."

Judge von Dadelszen said gay adoptions were allowed in England, Wales, Scotland, Western Australia, the Australian Capital Territory, and several European countries, United States states and Canadian provinces.

He said research "does not support any scientific basis for discrimination against homosexuals with regard to fitness to parent".

"In a 2003 study it was shown that there was no evidence of gender confusion in boys and girls brought up in lesbian-led families.

"Other criticisms centre on the belief that having homosexual parents may produce [gay] children ... Putting aside the obvious implication in that statement [that children turning out to be gay is wrong], studies have shown that the range of sexual orientation among children raised by same-sex couples is no different from that for children of heterosexual families."

He suggested the Families Commission should promote a change to the law. Chief Families Commissioner Jan Pryor has since agreed to meet the judge in October to discuss the issue.

Labour's current shadow justice minister Lianne Dalziel said she would write to Mr Power suggesting instead that the Law Commission should be asked to review both adoption and other legal rules around parenthood in the context of surrogate pregnancy and other new technologies.

But United Future leader Peter Dunne said legalising gay adoption would be contrary to "the view of the mainstream".

* Landmarks

1986: Homosexual relations between adults decriminalised.

1993: Human Rights Act bans discrimination on grounds of sexual orientation.

2004: Homosexual couples allowed to form legal civil unions.

2004: Care of Children Act allows gay couples to get parenting and guardianship orders.

2009: Judge says gay couples should be allowed to legally adopt children.