Released last month, the document maintains traditional teaching that marriage is between a man and a woman.
The report was slammed as a "very significant betrayal of trust" after years of shared conversations between liberals and conservatives in the Church.
General Synod will debate the report on Wednesday before a 'take note' vote. The Lesbian and Gay Christian Movement (LGCM) has launched a campaign to return a no vote.
If successful it would be a stunning defeat for the House of Bishops.
LGCM wants all its members and supporters to write to their local Synod members and bishops and urge them to vote against the report because it is "dangerous and inadequate".
Chief Executive Tracey Byrne told Premier the group was examining all options in order to succeed in a vote against the report.
It is possible the vote could be broken down and taken separately in each sector of Synod meaning a defeat is much more likely.
She said there were options that would be "most effective and enable most people to give a voice to their feelings, on both sides of this debate".
However, speaking on Premier's News Hour, General Synod member Canon Jonathan Ford stressed it would be foolish to veto the report.
"This report does not bring a halt down on anything," he said, "in no way does it describe itself as a final word."
"What it is doing is authorising a whole range of fresh initiatives which I think has been over looked.
"It's certainly going to look at liturgy."
