The Bishop of Salisbury, the Rt Rev Nicholas Holtam, suggested Christians should rethink their interpretation of Scripture in light of changing attitudes towards homosexuality in society.
In a strongly worded intervention as members of the House of Lords prepare to debate the Governments draft legislation introducing gay marriage, Bishop Holtam told peers that allowing gay couples to wed would be a very strong endorsement of the institution of marriage.
Bishop Holtam previously opposed gay marriage, but is now the only diocesan bishop in the country to publicly favour the proposed new law.
In a letter sent to Lord Alli, a gay Muslim peer, and published in The Daily Telegraph, Bishop Holtam distanced himself from the Church of Englands official opposition to same-sex marriage, saying: Christian morality comes from the mix of Bible, Christian tradition and our reasoned experience.
For example, before Wilberforce, Christians saw slavery as Biblical and part of the God-given ordering of creation. Similarly in South Africa the Dutch Reformed Church supported Apartheid because it was Biblical and part of the God-given order of creation. No one now supports either slavery or apartheid. The Biblical texts have not changed; our interpretation has.
Bishop Holtams intervention comes as peers from all main political parties prepare to mount a last-ditch attempt to block the draft legislation, which has been championed by David Cameron.
The Church of England, which has 26 bishops in the Lords, formally opposes the move and there has been speculation that the Most Rev Justin Welby, the recently appointed Archbishop of Canterbury, will be among bishops voicing their concerns about the policy at the debate.
A statement issued by the Churchs House of Bishops and Archbishops Council last year and endorsed by the Archbishop, said same-sex weddings were against Anglican teachings and would undermine the state of marriage, as well as being divisive and legally flawed.
However, the statement prompted a groundswell of opposition within the Church and two suffragan bishops broke ranks to say it did not speak for them, nor for a substantial number of clergy and churchgoers.
