The Right Rev. Nicholas Holtam compared those who use biblical references to dismiss homosexual relationships to those in the past who used the Bible to justify slavery, The Daily Telegraph reported. He spoke at a conference in London on the church and homophobia.
Holtam's statement follows a letter from a group of senior clergy, including retired bishops and the deans of some cathedrals, that said the push for gay marriage is a sign of "God's grace."
"Experience might lead us to be cautious about the certainty with which moral positions are built with biblical support.
"Before Wilberforce, Christians in this country saw slavery as having biblical support for what was the God-given in the ordering of creation," Holtam said, referring to the great 18th-century abolitionist, William Wilberforce.
Britain now allows civil unions for gay couples. Conservative Prime Minister David Cameron has proposed extending that to marriage.
The Catholic Church is opposed to gay marriage. The Church of England, which ordains openly gay priests, appears to be split on the issue with most bishops urging the government not to take the step.