Catholic bishops have moved to call for a No Vote in the upcoming same-sex marriage referendum.

The leaders of dioceses across the country have issued pastoral messages this evening - offering their reasons for asking citizens to vote against the proposed amendment to the constitution on May 22nd.

Bishop of Kerry Ray Browne said he believes a 'Yes' vote will change the definition of marriage, adding "the union of two of the same sex is fundamentally different from marriage and should develop independently under a different name."

Bishop O'Reilly of Kilmore says it is a contradiction to minimise human differences. He argues a father is not the same as a mother, and says "the referendum on same-sex marriage would put the wishes of adults ahead of the rights of children".

In a pastoral letter on marriage to the people of Clonfert, Bishop John Kirby says, "as well as being Church people, we are citizens of the Irish State and we rightly play our part in the democratic decision-making process. Marriage is too precious a component of society to allow it to be changed without a clear understanding of what we are doing."

He also states that, "serious anti-gay bullying is still a factor in many aspects of life including in schools and in workplaces. There should be zero tolerance for any form of conduct or intimidation of this sort."

Bishop of Limerick Dr Brendan Leahy earlier warned that the proposed "major shift" in the Constitution will have implications for the role of marriage and family, but urged both sides to remain respectful of each other's view.

Bishop Leahy's been outlining why he individually, and as a signatory of the statement from the Bishops' Conference, cannot support this amendment to the Constitution.