"I think I'm just handing on the teaching of the Christian Church almost 2,000 years, for over 2,000 years, since Christ was on Earth, handing on his same teaching and doing my best to hand it on in a way that many people can hear it," he said.
"I think if the United Kingdom does go for and supports same sex-marriage, it is indeed shaming our country," O'Brien also said. "We're taking standards which are not just our own, but standards from the declaration on human rights of the United Nations where marriage is defined as a relationship between man and woman and turning that on its head, and saying that marriage is no longer marriage. We're trying to redefine something that has been known and revered for centuries and making it something different."
The Catholic Church in England has also intensified its campaign against the government. Church leaders said in a statement that "Same sex couples already enjoy the benefits provided by civil partnerships."
Extending marriage to include same-sex partnerships would fundamentally redefine the meaning of marriage, church officials said.
"A change in the law would gradually and inevitably transform society's understanding of the purpose of marriage," the statement reads. "It would reduce it just to the commitment of the two people involved. There would be no recognition of the complementarity of male and female or that marriage is intended for the procreation and education of children. We have a duty to married people today, and to those who come after us, to do all we can to ensure that the true meaning of marriage is not lost for future generations."
The Church of England has decried the idea as tantamount to legislating cultural change. Officials emphasized in a statement that the institution is "committed to the traditional understanding of the institution of marriage as being between one man and one woman."
The Church of England supports the way civil partnerships offer same-sex couples the same rights and responsibilities as married heterosexual couples, church representatives said. "Opening marriage to same-sex couples would confer few if any new legal rights on the part of those already in a civil partnership, yet would require multiple changes to law, with the definition of marriage having to change for everyone," the church said.
"The issue of whether marriage should be redefined to include those of the same-sex is a more complicated picture than has been painted. Arguments that suggest 'religious marriage' is separate and different from 'civil marriage', and will not be affected by the proposed redefinition, misunderstand the legal nature of marriage in this country. They mistake the form of the ceremony for the institution itself," the statement reads.
The British government launched a consultation earlier this month – to close in June – that proposes to "enable same-sex couples to have a civil marriage." The change in the law would not oblige any religious institutions to grant ceremonies of marriage to same-sex couples, as religious marriages "will continue to only be legally possible between a man and a woman," the government assured.
Same-sex couples in the United Kingdom were legally allowed to enter into civil partnerships since 2004. Passed under Prime Minister Tony Blair, the civil partnerships law grants same-sex couples equal access to national pensions, inheritances, tax breaks, and other rights enjoyed by married heterosexual couples.
Prime Minister Cameron, a Christian and married father of three, has called same-sex marriage a matter of basic human rights. His position on the issue gradually evolved after he won the party's leadership in 2005.
"I don't support gay marriage despite being a Conservative,'' Cameron said in a recent speech on the issue. "I support gay marriage because I am a Conservative.''
There are currently at least 12 openly gay members of parliament from the Conservative Party, more than all other British political parties combined, according to The Boston Globe. It has been suggested by British media that Cameron's support for gay marriage may be an attempt to attract the sympathy of younger voters, especially young urbanites.