The non-denominational education body, Educate Together, has rejected three options for removing the so-called 'baptism barrier' to school entry, and has given conditional support to the fourth.
Education Minister Richard Bruton recently opened a consultation on ways to limit or remove the role that religion plays in school admissions.
In its submission, Educate Together said approaches involving a catchment area, a nearest school rule or a quota system were unsatisfactory.
It "most fully supports" the option of outright prohibition on the use of religion as a selection criterion, but said it could not include any provision for parents to sign a declaration that they would support a school's ethos.
"It is abhorrent to suggest that parents 'sign a disclaimer' that states they understand and support the ethos of a school that they may only be sending their children to because they lack an alternative," the submission states.