The DUP has claimed to have gained more than 100 new members from the Ulster Unionist Party in the Lagan Valley constituency.
The occasion was to welcome the best known defectors
The latest defectors include party officers who handed in their resignations before attending a DUP rally in Lisburn's Orange Hall on Wednesday night.
The occasion was to welcome the best known defectors, Jeffrey Donaldson, Arlene Foster and Norah Beare, who left the UUP in December.
Mr Donaldson said: "Tonight I am not alone. In this hall this evening, are members of Ulster Unionist branches in this constituency - Dromore, Lisburn, Hillsborough, Drumbo, Hillhall, Dunmurry, Ballinderry - and they have handed in their resignations from the Ulster Unionist Party."
He said it was not easy to end membership of a party after up to 40 years of service.
"They recognise - as I have and Arlene and Norah have and as the voters undoubtedly have - that the Ulster Unionist leadership is no longer worthy to lead unionism."
He added: "There are many of the MLAs at Stormont who are beginning to say - even openly - that it is time for David Trimble to step down."
DUP deputy leader Peter Robinson said his party intended to secure a deal based on the democratic principles of unionism.
"Trimble's Vichy regime has been ousted. The new regime will not fall into the trap of the Trimble-ites, of succumbing to the blackmail of paying a ransom to reduce terrorist activity.
"You can choose Mr Adams. As far as we are concerned it is guns or government - not both."
Jeffrey Mitchell, the former vice-chairman of the Lisburn UUP association, said the party lacked direction.
"Five years down the line and we haven't even got decommissioning sorted out," he said.
"Our party has lost touch with reality."
Former association chairman Tom Kerr said: "For a number of years now the party leader has led us in the wrong direction within the Ulster Unionist Party," he said.
"He has given up core principles within Ulster Unionism."
Norah Beare said the UUP was "heading in the opposite direction of the groundswell of people".
However, UUP chairman James Cooper described the meeting as "cheap DUP propaganda".
"The fact of the matter is that when Jeffrey Donaldson and his colleagues left the party, they confidently predicted that there would be defections en masse to the DUP.
"There is absolutely no evidence in our party that this happened.
"If we count the number of resignations of which we are aware - which have been made to us in writing - there are no more than 20.
"In my own constituency - where Arlene Foster was supposed to bring with her reams of people - we have had three resignations."
Lagan Valley UUP assembly member Billy Bell said: "This meeting is yet another cynical attempt by the DUP to extract as much publicity from the defections of Mr Donaldson and Ms Beare.
"Frankly most people in the Ulster Unionist Party are bored and disinterested in the comments of our former members. Whatever constructive criticism they may have had has been replaced with sour grapes."