The Presbyterian Church in Ireland has adopted a new policy meaning anyone in a gay relationship cannot be a full member and children of same-sex couples cannot be baptised.
It comes after The Church in Ireland, which has 220,000 members across Northern Ireland and the Republic of Ireland, cut ties with its Presbyterian sister, the Church of Scotland, over its more liberal attitude to sexuality.
The decision was made on Friday after a contentious debate at the Church in Ireland's annual decision making General Assembly in Belfast.
Delegates adopted the policy, outlined in a report by the Church's doctrine committee.
The committee's report said: 'In light of our understanding of scripture and the Church's understanding of a credible profession of faith, it is clear that same-sex couples are not eligible for communicant membership nor are they qualified to receive baptism for their children.
'We believe that their outward conduct and lifestyle is at variance with a life of obedience to Christ.'
Former moderator Rev John Dunlop said it was a 'highly sensitive' issue and urged against the rules.
However, another former moderator, the Rev Stafford Carson, argued that the Church needed to make its position clear that it was not in favour of same-sex relationships.