The UK Supreme Court has rejected an attempt to overturn a court ruling in favour of same-sex and unmarried couples adopting.
Stormont's health minister Edwin Poots tried to challenge an appeal court's decision that paved the way for gay and lesbian couples to adopt children in the region.
A spokesman for the UK's top court said: "The Supreme Court of the UK has refused permission to appeal the Court of Appeal's decision in this matter."
At present a single gay or lesbian person can adopt in Northern Ireland but a couple in a civil partnership cannot.
A challenge to the legislation was mounted by the Northern Ireland Human Rights Commission, which was backed by an unidentified lesbian woman who wants to enter into a civil partnership and be able to adopt her partner's biological child.
Unmarried couples in Great Britain can apply jointly to be considered for adoption irrespective of sexual orientation. But anyone unmarried in Northern Ireland is only eligible for consideration as an individual.
Those in civil partnerships cannot apply individually or as a couple.
The Commission challenged the law on the grounds that certain provisions were unjustifiably discriminatory to those in homosexual relationships, in contravention of the European Convention on Human Rights.
The Court of Appeal in Belfast ruled in the Commission's favour and against Mr Poots's Department in June.
The Department then applied for permission to appeal to the Supreme Court on a point of law.
The Supreme Court spokesman added: "The Supreme Court issued an order on 22 October 2013 stating that the application did not satisfy the criteria of raising an arguable point of law of general public importance."