The Child Poverty Action Group says it is considering whether to seek leave to go to the Supreme Court to challenge a Court of Appeal decision on the Working for Families tax credit.
The Court of Appeal has dismissed an appeal against a ruling rejecting the group's bid to have the tax credit declared unlawful under human rights legislation.
The group says the in-work tax credit discriminates against children in beneficiary families because it is available only to working parents.
The Court of Appeal decision follows unsuccessful court action in the High Court and at the Human Rights Review Tribunal.
The higher court decided the credit materially disadvantages beneficiaries, but not enough to breach the Bill of Rights.
Child Poverty Action Group economic spokesperson Susan St John says that gives some hope.
"The Court of Appeal has actually acknowledged the discriminatory nature of the in-work tax credit and actually that's quite a high test," she says.
"Unfortunately they didn't go further and say that that was unlawful because they said it could be justified in terms of its objectives."
The group says it has 21 days to seek leave to appeal at the Supreme Court and will closely examine the decision before then.