The Church of England's governing General Synod is about to vote on whether to allow women to become bishops.
The move has been backed by the Archbishop of Canterbury-elect, Rt Rev Justin Welby, who is expected to speak during the debate to show his support.
The vote is considered to be the Synod's biggest decision since it approved the introduction of female priests 20 years ago.
The legislation has been backed by 42 out of the 44 Church of England dioceses, but needs a two-thirds majority from the 470-strong body made up of bishops, clergy and laity before the legislation is passed on to parliament, paving the way for the first women bishops in 2014.
If the legislation is rejected, it may be up to seven years before it can be debated and voted on again.
Most believe the vote will pass through the houses of bishops and clergy, but will be closer in the vote by the Synod's lay members.
During the first day of the three-day Synod meeting, Julian Henderson, archdeacon of Dorking, urged members to avoid hostility when making their decision.
"Inevitably there is an atmosphere of tension as we allow the process of voting to decide the way forward.
"Whichever way the debate and voting goes, there will be anxiety and emotion, but let's ensure we handle that moment with grace to one another and faith that the Lord is fulfilling his promise to build his church and the gates of hell shall not prevail against it."
The outgoing Archbishop of Canterbury, Dr Rowan Williams, has joined Bishop Welby in expressing his support for woman bishops, warning the Church that a failure to pass the legislation would lead to "a period of continued and perhaps intensified internal conflict".
More than 1,000 Church members have also signed an open letter urging the Synod to vote in favour of allowing women to enter the bishopric.
The letter, published in the Independent, said: "Just as the churches have repented of our historic anti-Semitism and endorsement of slavery, so we believe that we must now show clearly that we no longer believe women to be inferior to men."
This view is not shared by all in the Church. Lay member Emma Forward told the BBC that a vote in favour of women bishops would "go against the Church and the future of the Church".
She added: "We're looking for really constructive ways to work forwards, and this legislation that we have in front of us doesn't offer that. And that's why a 'no' vote is essential."
Lindsay Newcombe, vice-chair of Anglo-Catholic group Forward in Faith and fellow lay member, added: "I am one of many in the Church of England who don't think women bishops are the way forward, and I don't think this measure [in particular] is the right way forward.
"My concern also is that the Church of England is part of the worldwide church and as one part of the Church I don't think we have the authority to make this change without the agreement of the rest of the Church."
Other members of the Church, including some Anglo-Catholics and conservative evangelicals, have long opposed the legislation. Currently 944 out of 12,792 parishes in the Church of England refuse to have a woman vicar.