Gay marriage: Church in Wales bishops want exemption
The Church in Wales has warned that any exemptions allowing the Church of England not to conduct gay marriages must apply to it as well.
The UK government is consulting on whether to change the law to allow same-sex couples to marry by 2015.
The Church of England warned that government pledges to exempt religious organisations from the change may not survive a legal challenge.
Bishops in Wales say they are in an "almost identical" legal position.
But they said their concerns were the same as those in England, and that Wales should be specifically included in any provisions for the Church of England under the proposed legislation.
The Welsh bishops said the current laws relating to civil partnerships for gay couples were sufficient, and going further to allow them to marry would not add to these, but risk the dangers of significant confusion and debate.
"It is not at all clear in what ways same-sex marriage will be different in substance from existing arrangements for civil partnerships," they said.
"They already appear to be in all respects the same, in the rights and responsibilities conferred on the parties; and with only very minor distinctions in the methods of registration, or the reasons for dissolving the relationship.
"Nor is it clear what will be the purpose of retaining the category of civil partnership alongside same-sex marriage, especially since it is not proposed that heterosexual couples be allowed to enter into a civil partnership.
"In the context of equality of access to registered relationships, this appears to create a new inequality."
Civil partnerships were introduced in 2005 to give same-sex couples the same legal rights as married couples, but the law does not allow such unions to be referred to as marriages.
The UK government has rejected the Church of England's assertion that the consultation exercise, which closes on Thursday, was "flawed, conceptually and legally".
The prime minister's spokeswoman confirmed that the government still intended to legislate on gay marriage by the end of this parliament, and had taken legal advice on the likelihood of a challenge to the European court before drawing up the proposals.
Andrew White, director of the gay rights organisation Stonewall Cymru, said he hoped the Church in Wales would reconsider its stance, but noted that the proposals wouldn't compel clergy to conduct same-sex marriages.
"It's an important issue of religious freedom that any denomination should be free to decline to celebrate long-term same-sex partnerships," he said.
"Conversely, that means that a church should not be entitled to prevent other institutions or the state from recognising them either.
"We trust the Church in Wales will eventually reconcile itself to same-sex marriage, and note the Archbishop of Wales' recent remarks suggesting that his Church should be more welcoming of gay couples.
"The church's response points out that being in a same sex relationship currently excludes people from the institution of marriage.
"We're very glad that the government are seeking to address this fundamental unfairness through the extension of civil marriage to same sex couples."