An overwhelming majority of churches would not host same-sex weddings even if the law is changed to allow it.
Almost all the major Christian denominations have vowed not to officiate for gay marriage, as have most other religious groups.
The same-sex marriage bill passed its first reading in Parliament this week and must now pass two more readings before it can become law.
But Catholics, Anglicans, Baptists and many other smaller denominations have already joined Muslims, Hindus, Sikhs and Orthodox Jews in prohibiting gay marriages on their turf.