The chair of the Referendum Commission says a Yes vote in the gay marriage referendum would not block the Oireachtas from passing laws that favoured opposite-sex couples.

But Mr Justice Kevin Cross says any laws would have to have a "good, fact-based reason" for giving extra rights to opposite-sex couples but not to same-sex ones.

Although the commission says the vote will not change Irish surrogacy law, No campaigners have continued to raise concerns that gay couples could be given an automatic right to surrogacy.

Mr Justice Cross told Newstalk on Wednesday there is no automatic right to have children, no automatic right to adoption and no automatic right to surrogacy in Ireland - and that will not change regardless of the result on May 22nd.

But Margaret Hickey of Mothers and Fathers Matter says there needs to be clear legal advice about giving gay couples the right to found a family.