The Tánaiste has ruled out a so-called 'conscience clause' for opponents of same-sex marriage.

Joan Burton says she cannot see any circumstances were businesses would still be allowed to discriminate on the basis of their own beliefs.

She was responding to calls from Dublin Archbishop Diarmaid Martin, who wants businesses to be able to turn down business from same-sex couples even if the referendum is approved in two months time.

He sees it as a way for businesses to opt out of providing goods or services for gay weddings if the referendum is passed.

But Ms Burton says that idea cannot be accepted if the public decides to vote Yes.

Earlier, a former Fianna Fail government minister said lawyers would be the only winners if the 'conscience clause' was included as part of same-sex marriage laws.

He told Newstalk Breakfast he is cautious about progress so far on the Yes side, as campaigners try to persuade people to vote their way in the referendum.