More than 30 Ulster Unionists in constituency of leader David Trimble have quit the party.
They staged a walk-out last night from the annual general meeting of his Upper Bann association.
The BBC is today quoting vice chairman of the association, Mr Garfield Gilpin saying Mr Trimble has move away from "traditional unionist principles" and is warning the party may collapse if the disenchantment continues.
"The wheels are falling off the machine. We are probably looking at several branches facing closure."
The UUP has been riven with dissent over Mr Trimble's policy of supporting the Belfast Agreement and his nearest rival - and a man many thought would be his successor - Mr Jeffrey Donaldson left the party after November's Assembly elections.
For the first time, the UUP came in second behind the Rev Ian Paisley-led Democratic Unionists. Mr Donaldson defected to the DUP along with other high-profile UUP members Ms Arlene Foster and Ms Norah Beare.
It has been claimed that around 100 members of Mr Donaldson's Lagan Valley constituency association defected along with him.