The Church of England will today vote on legislation to allow women into the episcopate.
The vote follows years of often painful debate amid strong opposition from traditional evangelicals and Anglo-Catholics.
There is provision in the draft Measure for alternative oversight for traditionalist parishes that request it.
However, some traditionalists feel that it does not go far enough in meeting their needs.
The legislation needs to have a two-thirds majority in each of the three Houses of Synod.
While bishops and clergy are expected to vote in favour, the vote in the laity is expected to be much closer.
If the legislation is approved, it will need approval from both Houses of Parliament and Royal Assent before coming back before General Synod as a Code of Practice.
However, if it falls today, the legislative process will have to start again from scratch and it will be years before a new draft legislation is brought back before Synod for final approval.
Opening the debate in Church House in central London this morning, the Archbishop of York, Dr John Sentamu appealed for "gracious magnanimity and attentive listening".
The Bishop of Manchester, the Right Reverend Nigel McCulloch urged Synod members to give the legislation "an emphatic yes".
He called upon Synod members to consider the legislation with one question in mind - "will God's mission and ministry entrusted to the Church of England be advanced better if this legislation is approved or if it is rejected"?
Explaining his support for the consecration of women, Bishop McCulloch said: "I believe that we have here a Measure which, whatever its imperfections - and all legislation has its imperfections - can be made to work.
"I believe that it will enable the Church of England to flourish; that it will enable women to exercise the leadership which the great majority of us recognise as God's gift to this Church.
"And I truly believe, despite all the understandable concerns from those with theological difficulties about the ordination of women, that it will enable them to continue to have an honoured place within the Church of England and make their own distinctive and valuable contribution to its mission."
Bishop McCulloch admitted the legislation fell short of what he and others had been seeking but appealed to Synod members to accept compromise.
"Had Synod wanted to insist that there was now only one acceptable view on this matter in the Church of England the legislation before you for approval today would have been shorter and simpler. That is of course what some here would have preferred.
"So let's not in this debate underestimate the degree of compromise and accommodation that they have made."
He warned that if the legislation fell today "it would be a shock to large numbers of people across the Church of England".
He continued: "It would be a devastating blow to the morale of many, not least our female clergy.
"It would be a major deterrent to continuing to attract into the ordained ministry able women - and many able men too.
"It would also, in my view, do real harm to the credibility and mission of the Church of England to the people of this nation. They simply wouldn't understand."
Speaking against the legislation, Canon Simon Killwick, of the Diocese of Manchester, said it would turn traditionalists into "second class bishops" and "second class Anglicans".
"It doesn't have to be this way," he said. "On two occasions in the last few years, we have come tantalisingly close to a lasting settlement."
He said all sides were desperate to move on from the "sad infighting" of the last few years.
However, he contended that the legislation would not be good for the Church of England and would not bring closure because it "does not provide a clear and lasting way forward".
The Code of Practice, he contended, would become a "new battleground" in the Church, with the contents being fought over for years.
He said the provision to accommodate the traditionalist parish's concerns represented a "vague concept of respect" that could result in legal disputes being fought out in secular courts.
Canon Killwick said traditionalists would be "forced" to be under the oversight or jurisdiction of women bishops.
Delegation to male bishops would be limited largely to the taking of services, functions of episcopal oversight like clergy appointments or licensing would be shared, rather than delegated, he said.
"The Code of Practice would be an insecure method of provision - bishops and others would only have to have regard to its guidance; they would not be under legal obligation to follow it.
"In particular, if they could show cogent reasons for not doing so, they need not adhere to the Code."
He continued: "This draft legislation is not fit for purpose. It will not deliver the clear and lasting settlement which will enable us to move on together.
"We should reject it and make it clear that proper provision for traditionalists has to be an essential ingredient of a new Measure.
"We could then begin discussions to lead us towards a new Measure which would make fair provision for all, a Measure capable of commanding consensus, bringing peace and unity of purpose."