The Presbyterian Church in Ireland has issued a strong plea for Christians to vote "no" in next month's referendum on gay marriage.

The Presbyterians have joined with the Catholic and Methodist churches in calling for a "no" vote in the referendum on the constitution which takes place on 22 May.

In a statement posted on its website, the church said: "The Presbyterian Church in Ireland upholds the historic – and Christian – view of marriage as exclusively between one man and one woman. We affirm that it is needed for the common good of society.

"In recognising the rights of all people within a democracy, we must include the rights of children, and the natural responsibilities of a father and a mother in their nurture. We believe the change proposed in the referendum denies these rights.

"A redefinition of marriage would establish new norms within our society, the implications of which have not been fully explored. We acknowledge that this is an intensely emotive subject and trust that all will engage in the debate with gentleness and respect as we approach the Referendum."

The referendum will be about two proposed amendments to the constitution, reducing the age of candidacy for President of Ireland from 35 to 21 and permitting same-sex marriage. Voters will be asked whether to add to the Constitution that "marriage may be contracted in accordance with law by two persons without distinction as to their sex."

The Government and all the main parties are backing a "yes" vote and polls indicated that more than three in four voters support the change to allow same-sex marriage.