Catholic bishops have demanded that politicians reject marriage equality for gay couples in Northern Ireland, as Stormont prepares to debate the motion on Tuesday.
Equal marriage is an "inappropriate" use of the principle of equality, a letter from the Bishops said, adding" the proposed marriage equality motion before the assembly effectively says to parents, children and society that the state should not, and will not, promote any normative or ideal family environment for raising children.
"It therefore implies that the biological bond and natural ties between a child and its mother and father have no intrinsic value for the child or for society."
The open letter was signed by the head of the Irish church Cardinal Sean Brady and six bishops.
"We believe that the state should urgently provide more and better services in support of marriage in which mothers and fathers can provide the optimum loving and stable environment for children to grow and flourish," it continued, adding that same-sex relationships were already comprehensively provided for in legislation through their recognition as civil partnerships and associated equality legislation.
The Church of Ireland also restated its position on the issue, saying that "according to our Lord's teaching, that marriage is in its purpose a union permanent and life-long, for better or worse, till death do them part, of one man with one woman, to the exclusion of all others on either side".
The first gay weddings took place in England and Wales last month and Scotland passed a similar law in February, with the first same-sex marriages are expected there in October.
In Northern Ireland, with a greater proportion of Catholic and Protestant churchgoers than other parts of the UK and at times a more conservative social culture, any change would be more controversial.
The Stormont assembly motion tabled by Sinn Fein called on the Democratic Unionist Minister of Finance and Personnel, Simon Hamilton, to introduce legislation to guarantee that couples of any sex or gender identity receive equal benefit.
It proposed: "That this Assembly notes that other jurisdictions on these islands have moved forward with equal marriage rights for same-sex couples; believes that all couples, regardless of gender or sexual orientation, should have the same legal entitlement to marry and to the protections, rights, obligations and benefits afforded by the legal institution of marriage."
The motion also said religious institutions should have the freedom to decide whether or not to conduct same-sex marriages.
Sinn Fein Stormont MLA Caitriona Ruane said other jurisdictions are moving forward to ensure marriage equality for all.
"The North should not be left behind. Giving all couples equal marriage rights under the law does not threaten anyone's beliefs, religious or otherwise.
"Churches are free to define marriage as they wish but the state has a duty to treat all citizens equally."
The Republic of Ireland is set to have a referendum on equal marriage, with Europe's "father of gay marriage", the former Dutch MP Boris Dittrich, telling HuffPost UK last week that he expected Ireland to be the next country to adopt equal marriage.