A Roman Catholic charity said it might close its adoption services after a tribunal ruled that it cannot refuse to help gay couples adopt.
Catholic Care, the care agency for the Diocese of Leeds, has already been told by the Charity Commission it cannot opt out of equality laws that force it to offer adoption services to homosexuals.
Catholic Care believes more children will be left waiting for adoption because of the ruling
It had asked the Charity Commission for permission to amend its constitution so it could lawfully decline the services to same-sex couples.
But the commission refused and the charity unsuccessfully appealed against the decision made at a charity tribunal last year.
It then took the case to a higher tier tribunal which on Friday upheld the original ruling.
The charity has spent more than three years arguing that it will have to give up its work finding homes for children if it is forced to comply with the regulations, which it says clash with Roman Catholic doctrine.
Following the ruling, it said: "Without the constitutional restriction for which it applied, Catholic Care will be forced to close its adoption service.
"In doing so, it will be joining many other faith-based adoption services that have been forced to close since 2008.
"The reason for this is that the services permitted by the current constitution are in conflict with the aims of the charity.
"It is Catholic Care's view that this will reduce the number of adoptive parents available and the number of children left waiting for adoptive parents will continue to increase."
The charity added that it will "take time to consider the decision in detail" and decide on its next steps.
Upholding the decision that the Catholic Care's stance was unjustly discriminatory, Mr Justice Sales said: "The charity had failed to show that there were sufficiently weighty reasons to justify the discrimination it proposed to engage in.
"The fact that same-sex couples could seek to have access to adoption services offered elsewhere tended to reduce somewhat the immediate detrimental effect on them, but it did not remove the harm that would be caused to them through feeling that discrimination on grounds of sexual orientation was practised at some point in the adoption system."
The tribunal concluded the charity's legal argument was sound and said the law does allow discrimination in certain circumstances. But it found there was not a sufficient reason to overturn the original decision.
Catholic Care has the option to fight the decision in the Court of Appeal.