The Humanist Association of Ireland is calling for an end what it says is discrimination in State funded schools against children who are not baptised.
It has launched an advertising campaign, with ads in train stations, bus-shelters and other prominent locations around the country.
Humanist Association of Ireland director Brian Whiteside, said that more Irish people are having secular weddings, so it would be logical to assume that those people do not wish to baptise any children they may have.
"Now, we've got a growing number of who just simply aren't religious, and they're quite open about it," he said.
"Last year, one third of couples getting married got married in non-religious ceremonies, and I think it's fair to ask the question: 'What sort of schools would they want for their children?'."
Dr Frank Hurl of Catholic Comment said that the only time it becomes an issue is if a school is oversubscribed.
"I think the only time that a baptism cert would come into play is when there's oversubscription in a particular area, and that's really an issue for the Department of Education rather than the local school," he said.