If same-sex marriage is passed in the Republic of Ireland, the Catholic Church has threatened to stop performing legal marriages.
They would remove around 4,000 priests from the register of Marriage Solemnisers.
Any marriage ceremonies or blessings they carried out would not be legally recognised.
It would mean that Catholic couples wishing to get married under the Catholic Church would have to have both a civil ceremony and a religious ceremony.
A statement to the Irish Constitutional Convention reads: “It is important to note that in Ireland the Church and State co-operate closely in the solemnisation of marriages and that in excess of 70% of marriages in the Republic of Ireland are celebrated by couples choosing the Christian celebration of marriage with both elements taking place within the same ceremony.
“Any change to the definition of marriage would create great difficulties and in the light of this if there were two totally different definitions of marriage the Church could no longer carry out the civil element.”
The Republic of Ireland is set to vote on May 22 on a proposal to introduce civil same-sex marriage.