The Church of England can no longer play "happy families" over the deep divisions that exist on the gay issue, according to leading conservatives.
Andrew Symes of Anglican Mainstream, the conservative evangelical organisation, said he was not surprised that the Reform grouping had pulled out of the "shared conversations" on human sexuality.
He accused the Church of England leadership of a "flawed, manipulative and dishonest process where the result appears to have already been decided."
The latest part of the process took place at a recent meeting of the Church's bishops, when gay and transgender clergy and laity shared their stories with the bishops who were then split into small groups and urged to open up about their own sexuality.
The Bishop of Buckingham Alan Wilson subsequently claimed in a new book that as many as one in ten bishops were secretly gay. The campaigner Peter Tatchell has threatened to "out" these bishops if they do not out themselves.
The latest statements from the evangelical wing show how deep the divisions go and how difficult if not impossible it will be to bring about reconciliation.
Mr Symes said: "When the facilitated conversations, now known as shared conversations, were first mooted, many Anglicans who take an orthodox and conservative position on sexual morality believed that this would be a good opportunity to express their views clearly, hear opposing views, and tease out the profound theological and philosophical differences underlying the approaches to the Christian faith."
He predicted that some kind of separation might need to occur within the Church of England, but said this could be done with "good disagreement", without the rancour and litigation that marked the process in North America.
He warned that the recognition of all different theological positions as equally valid for Christians was never going to work.
"The Conversations have as a clear aim the establishment of two integrities within the C of E, where those who believe same gender sexual relationships are sinful, and those who believe they are from God and should be celebrated, should learn how to live together in the same church with good disagreement," he said.
"But given the pressure from Government, media and the prevailing culture it is very difficult to see how the conservative view on sexual ethics would continue to be tolerated if the C of E changed its policy to allow the blessing, and perhaps later, marriage of same sex couples in those churches that wanted to accept this."
Mr Symes added: "What we need now is not pretend 'happy families', but an honest, serious discussion about the future of the Church of England given the unresolveable differences that exist."
Earlier, the Reform council called on its members not to participate in the conversations.
Preb Rod Thomas, the chairman, said: "It is difficult to see how the process of shared conversations can command credibility if those who are most committed to the Church of England's official teaching are in effect excluded.
"If this project is not to collapse, then decisive intervention from the House of Bishops is needed now. The shared conversations must acknowledge that Scripture remains authoritative for the Church of England and that the outcome of the conversations is genuinely open-ended. Unless that is clarified and the recently announced new objective is withdrawn, we cannot see a way forward."
Reform also called for Bishop Wilson to be admonished for "his refusal to uphold the teaching of the church and guidance of the House on matters of sexuality."