The current ban on gay and unmarried couples adopting in Northern Ireland is in the child's best interests, the Court of Appeal heard today.
Attorney General John Larkin QC said research showed families headed by two biological parents in a "law conflict marriage" to be most beneficial.
The Stormont government's chief legal adviser is seeking to overturn a landmark ruling that the prohibition is unlawful.
In October last year the High Court held that the ban based on relationship status discriminated against those in civil partnerships and breached their human rights.
Mr Justice Treacy found excluding some would-be parents solely on their relationship status narrowed the pool of potential adopters and could not be in the best interests of children.
His verdict came in a legal challenge mounted by the Northern Ireland Human Rights Commission.
The body is seeking to force a legislative change to bring adoption laws into line with the rest of the UK.
Unmarried couples in England, Scotland and Wales can apply jointly to be considered for adoption, irrespective of sexual orientation.
But anyone unmarried in Northern Ireland is currently only eligible for consideration as an individual.
Those in civil partnerships cannot apply either individually or as a couple.
Judicial review proceedings centred on the blanket ban imposed on same-sex and unmarried couples by the Adoption (Northern Ireland) Order 1987.
The Commission was backed by an unidentified lesbian woman who wants to be able to adopt her partner's biological child.
The women, who have been in a relationship for four years, also wish to enter a civil partnership to signify their commitment.
Lawyers for the Commission argued that the legislation was discriminatory and breached family life considerations under the European Convention on Human Rights.
Representing the Department of Health in an appeal against the High Court ruling, Mr Larkin today set out two main points in his case.
"The current law on adoption in Northern Ireland, including the present eligibility criteria, best reflect the interest of children here," he said.
"Secondly, if there is to be a different structure to our law on adoption such a change should come from the Northern Ireland Assembly and not, with respect, from the learned trial judge."
The three senior judges hearing the appeal were told the Department's position was based on research that showed children are most helped by a "family headed by two biological parents in a low conflict marriage".
The Attorney General argued that child welfare must come first.
"The issue of the best interest of children in the field of adoption concerns the rights and interests of children, and is not apt for consideration through the prism of any suggested right of any adult person to adopt a child," he said.
He set out how the woman involved in the case claimed she and her partner have suffered discrimination.
She also stated that she has been denied access to services simply because she is gay.
But Mr Larkin claimed her assertion came "dangerously close to embarking on a notion that adoption is a way in which services to adults are provided".
He insisted: "They are not services and the Department refuses to consider them that way."
The appeal, listed for a three-day hearing, continues.