Taoiseach Enda Kenny has said he is confident that the same-sex marriage referendum will be passed, but said this will only happen if people turn out and vote.

Mr Kenny was speaking on The Pat Kenny Show on Newstalk.

He said the referendum had nothing to do with surrogacy, fostering or adoption.

The Taoiseach said it was simply a question about extending the civic law to accommodate two men or two women getting married.

Mr Kenny said the referendum was not just about gay people but was also about their extended families and communities, and removing discrimination from this area of Irish life.

He said he did not regret not "tidying up" the surrogacy issue in advance of the referendum.

Mr Kenny said a Yes vote would send out the signal that society had changed and that Ireland offers equality to all its citizens.

He said a No vote would be a huge disappointment.

On the vote on lowering the age of presidential candidates, Mr Kenny said people should have the right to contest for the highest office in the land regardless of age.

He said he would not consider going for the office himself.

Dublin Gaelic footballer Ger Brennan has said he is in favour of marriage equality but will be voting No in the same-sex marriage referendum because of his concerns about surrogacy and assisted human reproduction.

He said he favours granting same-sex couples an equal right to marry, provided that the Constitution protects children who will be born as a result of surrogacy agreements.

Meanwhile, world-renowned novelist Colm Tóibín has urged a Yes vote, saying gay and lesbian teenagers in particular need to be reassured that they have an equal right to marry.

He said he believes gay people have for too long been forced to live in the shadows.

Minister for Jobs, Enterprise and Innovation Richard Bruton said the Government is confident but not complacent about the marriage referendum proposal being accepted.

He said there would be work to be done right through until 22 May, and it would be about persuading people.

Asked if he accepted concerns by some on the No side that the funding provided to organisations campaigning for a Yes vote might be an attempt to buy a Yes vote, Minister Bruton said he did not accept this at all.

He said people would make an individual decision on this issue.

Irish psychologist Dr Maureen Gaffney told a Yes Equality gathering that children of same-sex couples develop just as well as the offspring of male-female couples.

Dr Gaffney said a review of the international research literature led her to conclude without hesitation that not one single study shows any significant difference in the emotional, educational and social development of children reared by gay and lesbian couples.

She criticised some No campaigners for loading the problems of surrogacy onto the shoulders of the gay and lesbian community as if they had not enough problems already.

Meanwhile, Iona Institute Patron and psychiatrist Professor Patricia Casey has said that Maureen Gaffney needs to withdraw remarks likening No voters to Nazis and racists

Professor Casey said: "What Dr Gaffney has said is appalling and must be withdrawn immediately. She claims she is not making a direct comparison between No voters on the one hand, and Nazis and racists on the other, but that is exactly what has done.

Professor Casey said: "She puts opposition to same-sex marriage on precisely the same moral level as Nazism and racism. Her comments show a total lack of respect for those voting No."

She said: "It shouldn't need to be spelled out, but believing in the family of man, woman and child based on marriage is not remotely comparable to racism."

"The differences between skin colour are absolutely irrelevant to the nature of marriage or to anything else, but the differences between men and women, and mothers and fathers are intrinsic to the nature of marriage." She added.

Professor Casey continued: "Is Dr Gaffney seriously suggesting that believing in the differences between men and women and mothers and fathers is the moral equivalent of racism and Nazism?"

Separately, a Dutch psychologist has told a No campaign meeting that a study shows homosexual people in Amsterdam are promiscuous and that their relationships last just 18 months on average.

Speaking at a press conference organised by the Alliance for the Defence of the Family and Marriage, Dr Gerard van den Aardweg quoted from study in Amsterdam showing the average duration of a homosexual relationship was a year-and-a-half.

He said that during the first year of a stable relationship other sexual contact was made and that it was practically unknown for any such relationship to last more than five years.