The Tánaiste has ruled out a so-called "conscience clause" for opponents of same-sex marriage.
Joan Burton said she cannot see any circumstances where businesses would still be allowed to discriminate on the basis of their own beliefs.
"If the people in their wisdom decide to agree with the marriage equality referendum, then it will be on the basis of marriage equality.
"I don't actually see how you could operate something which would exclude some people or some institutions from the operation of marriage equality."
She was responding to calls from Archbishop Diarmuid Martin, who wants companies to be able to turn down business from same-sex couples - even if the referendum is approved in two months.
The Tánaiste said that idea cannot be accepted if the public decides to vote yes.