Catholic bishops in Northern Ireland are writing to assembly members urging them to vote against a motion which would legalise equal marriage.
The Stormont Assembly will debate the issue on Monday 29 April.
The proposed motion is being pushed by Sinn Fein following an overwhelming vote in favour of a referendum on legalising same-sex marriage in the Republic of Ireland.
Father Bartlett, from the Catholic Council for Social Affairs, told the BBC: “Any debate about this matter from a Christian point of view has to be framed in terms of respect, love, kindness towards each other and for each other as human beings and respect the dignity of each other.
“Mums and dads are important and that difference between men and women in the rearing of children is important and society has always recognised that and given it a special place.”
Northern Ireland’s Presbyterian Church has also written to assembly members re-stating its opposition to marriage equality.
There will be a demonstration, organised by Equal Marriage Northern Ireland, outside of the Stormont Assembly on Monday to coincide with the debate.