The Lisburn branch of the Ulster Unionists has today called on party leader Mr David Trimble to resign.
It issued the call after their local MP, Mr Jeffrey Donaldson, quit the party for the Rev an Paisley's Democratic Unionists.
Two other former Ulster Unionist Assembly members joined him in the DUP this week - Lagan Valley MLA Ms Norah Beare and Fermanagh and South Tyrone MLA Ms Arlene Foster.
After a branch meeting, UUP members in Lisburn criticised members of the party who "were relentless in pursuing the expulsion" of Mr Donaldson and Ms Beare.
They blamed Mr Trimble for the party's performance in the November Assembly election, in which the Ulster Unionists fell behind the DUP and Sinn Fén in the popular vote for the first time.
"The unionists of Lagan Valley voted overwhelmingly for candidates opposed to the Belfast Agreement," the branch declared. "They mandated Jeffrey Donaldson and his colleague Norah Beare to go into the Assembly and work with other unionists of a like mind to secure a better Agreement.
"In so doing they have our full and unequivocal support. We believe that David Trimble is primarily responsible for the losses sustained in the Assembly elections by the UUP", the branch said.
PA