Groups campaigning against same-sex marriage claimed the Referendum Commission chairman "contradicted" himself by insisting the passing of the constitutional change is not about surrogacy.
During an interview yesterday morning, Justice Kevin Cross said it was the commission's view that the referendum is not about either surrogacy or adoption.
However, Justice Cross added that, if surrogacy laws are passed in the future, same-sex and opposite-sex couples will have equal access unless it can be proven this is not in the best interests of the child.
He admitted he previously had "not spelt it out clearly enough" but believed both sides of the debate accepted the commission's ruling on the divisive issue.
"The referendum is about marriage, and who may marry, and who may not marry. It is not, in our view, about adoption. It is not, in our view, about surrogacy," the judge told RTÉ Radio One.
"If the Government legislate to allow surrogacy, same-sex and opposite-sex couples would have the same access to surrogacy unless it is shown there is a rational basis for any differentiation," he added.
Campaigners for a 'Yes' vote later released a statement quoting Justice Cross saying the referendum was not about surrogacy but without mentioning his comments on equal access for all couples if laws are passed.
Mothers and Fathers Matter spokesman Tim Finnegan later claimed Justice Cross "contradicted" previous remarks he made on surrogacy.
He claimed the judge said in an interview that it will be "difficult to image" how a future Oireachtas could give a stated preference in law for a child to have a mother and a father if the referendum passes.
Mr Finnegan said it was important to distinguish between the statutory and constitutional effects of passing the referendum.
"No person other than an Oireachtas member has any direct say on statute law. What we are being asked to do on Friday as the electorate is amend the Constitution and that will have constitutional effects and that will decide to what extent the Oireachtas may or may not decide to regulate or form laws in relation to adoption, surrogacy and donor-assisted human reproduction," Mr Finnegan said.
A Referendum Commission spokesman said: "There is no contradiction between what the chairman said today and what he and the commission have said throughout the referendum campaign."