The Quakers have supported same-sex unions for more than two decades
One of the UK's oldest Christian denominations - the Quakers - looks set to extend marriage services to same-sex couples at their yearly meeting later.
The society has already held religious blessings for same-sex couples who have had a civil partnership ceremony.
But agreeing to perform gay marriages, which are currently not allowed under civil law, could bring the Quakers into conflict with the government.
The issue of active homosexuality has bitterly divided Churches.
But the BBC's religious affairs correspondent Robert Pigott said the Quakers had been more prepared than other groups to reinterpret the Bible in the light of contemporary life.
The Quakers - also known as The Religious Society of Friends - are likely to reach consensus on the issue of gay marriage without a vote at their annual gathering in York on Friday.
They will also formally ask the government to change the law to allow gay people to marry.
Quaker registrars, like rabbis and Church of England priests, have the authority to marry heterosexual couples on behalf of the state.
But many British Quakers feel it is wrong to exclude a religious commitment from civil partnerships and want the right to marriage extended to same-sex couples too.
The Quakers has welcomed same-sex unions for more than two decades, allowing local groups to celebrate same-sex commitments through special acts of worship.
But within Britain's Christian community more widely, the issue of homosexuality has caused major confrontations.
Most recently, the Bishop of Rochester, the Right Reverend Michael Nazir-Ali, told a newspaper that homosexuals should "repent and be changed".