The Council also sought confirmation from the Premier that, should a same-sex marriage bill be introduced by a private member or another political party, the bill would not be given priority and Coalition members would not be given a conscience vote.
The move comes after Tasmanian Premier Lara Giddings announced on Sunday that her government would pursue legislative reform to allow same-sex marriage in Tasmania.
NSW Council of Churches President, Revd Dr Ross Clifford, said such a move would undermine longstanding Australian cultural and heritage values, and lead to chaos and confusion with respect to the recognition of marriage across state borders.
"The Tasmanian plan indicates that a federal same-sex marriage bill is expected to fail due to lack of public support for such radical social policies," Dr Clifford said.
"There is no doubt that State legislation allowing same-sex marriage would be morally and administratively problematic, and we call on Premier Barry O'Farrell to rule it out in NSW. We also call upon the NSW Premier to become a party to any High Court challenge the Tasmanian Government pursuing such a divisive initiative," he said.
In February 2012 the NSW Council of Churches unanimously endorsed a Joint Statement on the Significance of Marriage, which states:
Marriage is the lifelong commitment and faithful union of one man and one woman. As such, marriage is the natural basis of the family because it secures the relationship between biological parents and their children.
As Christian leaders representing different denominations or churches, we join together and affirm our shared commitment to promote and protect marriage. We honour the unique love between husbands and wives, the vital place of fathers and mothers in the life of children, and the corresponding ideal for all children to know the love and role modelling of a father and a mother.
Marriage thus defined is a great good in itself, and it also serves the good of others and society, as it has done for thousands of years. The preservation of the unique meaning of marriage is therefore not a special or limited interest, but serves the common good, particularly the good of children.
We call on our Federal and State Governments to protect this definition of marriage in Australian law, and not change the meaning of marriage by adding to it different kinds of relationships.