During the hearing, which finished on Friday, the commission argued it would be a "serious and demeaning act of discrimination" for the charity to restrict its adoption services to heterosexual, married couples.
The charity appealed to the tribunal to quash the commission’s ruling, made in August last year, that it could not change its objects to prevent same-sex couples from using its adoption service. Catholic Care argued that failing to change its objects would force it to close its adoption service because it would lose its funding from the Catholic church.
The commission’s barrister, Emma Dixon, said at the hearing: "The exclusion of same-sex couples is a particularly serious and indeed a demeaning act of discrimination. Weighty reasons would be needed to justify discrimination on the grounds of sexuality."
Dixon said religious belief was not a justification for restricting its services to heterosexual couples.
"The Charity Commission was right to conclude that there were no substantially weighty reasons to justify the exclusion of gay and lesbian couples," she said.
Christopher McCall QC, the barrister acting on behalf of the charity, argued that section 193 of the Equalities Act 2010 allowed organisations to discriminate on the grounds of sexuality if this was "a proportionate means of achieving a legitimate aim".
He said the charity accepted that discrimination was "detrimental in itself", but that its only alternative was to close its adoption service, which would be a bigger loss to the community.
"This service can only be provided on the grounds that it is not open to all," he said. "It is beside the point to argue that it would be better for all to be able to access the service, because that couldn’t happen. We are not proposing any more discrimination than is necessary. What is section 193 for if not this?"
In response to McCall, Dixon said: "There is no evidence as to whether donors would give if the service was open. They haven’t tried. Section 193 would apply if there was a rational link between the restriction and the charity’s aim, and that is what is missing here. The fact that the charity might close is not a justification for discriminating."
Alison McKenna, principal judge of the charity tribunal, said it would make its decision in about a month.