An unmarried Northern Ireland mother refused a widowed parent's allowance following the death of her partner is to take her legal fight to the UK's highest court.
Last month senior judges in Belfast overturned a ruling that Siobhan McLaughlin was discriminated against on the grounds of her marital status.
But she is now attempting to challenge their findings at the Supreme Court in London.
If ultimately successful, the potentially landmark case could set a precedent for bereaved cohabiting parents across the UK to receive extra payments, costing the government hundreds of millions of pounds.
Ms McLaughlin brought a test case against Stormont's former Department for Social Development after being refused the benefits because she was neither married nor in a civil partnership at the time of her partner's death.
The couple lived together as man and wife for 23 years before he died in January 2014.
They had four children together and for whom she remains sole provider.
A key component of the family income comes from state benefits.
Ms McLaughlin would have been entitled to the further allowances under the Social Security Contributions and Benefits (NI) Act 1992 had she been married.
Her barristers argued that the decision unlawfully discriminated against Ms McLaughlin due to her marital situation.
They also contended that it breached her private and family life entitlements under Article 8 of the European Convention on Human Rights.
In February last year a High Court judge ruled that the denial of benefits could not be justified.
He held that the rationale for the benefit applied equally to people in Ms McLaughlin's position as to married widows with children.
The purpose of the benefit was to diminish the financial hardship on families following the death of a parent, he found.
In his judgment the restriction amounted to a human rights violation by unjustifiably discriminating against Ms McLaughin on the grounds of her marital status.
However, lawyers for the Department appealed, arguing that the judge had wrongly decided the relationship of an unwed cohabitee was comparable to those married or in a civil partnership in considering the allowance.
The court heard how extending the benefit to surviving, unmarried parents - with an estimated cost of £21.6m per annum - was rejected by the British Government in June last year.
In December the Court of Appeal backed the Department after finding that the relationship of an unmarried co-habitee is not analogous with that of a spouse or civil partner in the context of a widowed parent's allowance.
Counsel for Ms McLaughlin, David McMillen QC, returned to court today to seek for leave to take a challenge the verdict to the Supreme Court.
Although Lord Chief Justice Sir Declan Morgan formally refused to certify a point of law of general public importance, he left the door open for her legal team to petition directly for a hearing in London.
Sir Declan said: "We recognise there are issues in relation in particular to comparators and justification, and no doubt the Supreme Court will give careful consideration if an application is made to it."
Outside court Ms McLaughlin's solicitor confirmed plans to take the legal step.
Laura Banks of the Citizens Advice Bureau said: "Our intention is to petition the Supreme Court directly for a hearing of this matter because we believe it's of significant public interest." ends