The leader of the Women's Coalition, Ms Monica McWilliams, has said Mr David Trimble's proposals were like a "bolt of lightning" hitting the peace process.
Ms McWilliams said the process was being "constantly picked at by rejectionists on both sides.
"That's got to change as of next week if we are going to rescue this process and start resolving it. I'm very concerned that the No camp are clearly putting it up to the rest of us, including those in the Ulster Unionists who want progress."
Ms McWilliams said she thought Mr Trimble's proposals "may have gone outside of what's in the agreement".
She called for the establishment of a contact group of pro-agreement parties within the Assembly. "That would prepare for this type of bolt of lightning," she said.
The Alliance Party's youth affairs spokesman, Mr Michael Long, accused Mr Trimble of jeopardising the process. He said Mr Trimble had "caved in" to anti-agreement forces within the UUP.
"How David Trimble can claim to continue to support the process while threatening to bring the whole thing down is beyond me."
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