The Church of England is standing against the government's plan to legalize gay marriage.
Prime Minister David Cameron supports a proposal allowing civil marriages for gay couples. But church officials oppose the proposal on the grounds that it historically has defined marriage as between a man and a woman.
Bishops argue that gay couples already have many of the legal benefits of marriage through a 2005 law recognizing civil partnerships.
They're concerned that churches will one day be required to perform same-sex marriages.
"To change the nature of marriage for everyone will be divisive and deliver no obvious legal gain given the rights already conferred by civil partnerships," church bishops said in an official statement.
"We believe that imposing for essentially ideological reasons a new meaning on a term as familiar and fundamental as marriage would be deeply unwise," they said.
The issue has caused friction between Cameron, who is allowing party members to vote their conscience on the legislation, and Deputy Prime Minister Nick Clegg, who expects all members of his Liberal Democrat party to support the change.
The church's paper was released on the day when the traditional marriage group Coalition for Marriage plans to bring to Cameron's office a petition with more than half a million signatures opposing the change.