Former Ulster Unionist MP Jeffrey Donaldson today confirmed his defection to Ian Paisley's ultra-hardline DUP.
Mr Donaldson and two other former Ulster Unionist Assembly Members, Ms Arlene Foster and Ms Norah Beare, quit the party before Christmas.
Mr Donaldson and his two followers appeared alongside the current-30-strong DUP assembly team at a press conference today.
They announced that they had decided to join the DUP after receiving an invitation to join Mr Paisley's negotiating team for the forthcoming review of the 1998 Good Friday Agreement.
Mr Paisley welcomed the defections and claimed could mark the start of an exodus from the Ulster Unionist Party into his party.
``I bid them welcome to the DUP,'' Mr Paisley said.
``I believe this is the beginning of large numbers of people who always voted Official Unionist who are now going to join with us.
``I hope to shortly announce a recruiting drive across the province so we can enlarge our party and prepare for what is coming in the days of the negotiations.''
Mr Donaldson today launched an attack on his former leader, David Trimble, and his supporters, claiming they had abandoned core unionist principles.
``I am proud to be part of a team capable of providing leadership to the unionist community, not like the leadership of the party I left.
``Not like a leadership which has no bottom line, a leadership which does not know how to lead the unionist community.''
Mrs Foster claimed the DUP was now the mainstream unionist party in Northern Ireland.
She insisted: ``There is no fight left in the UUP.''
The defections mean the DUP, which claims the Good Friday Agreement is finished, now has 33 seats at the putative Belfast Assembly and also becomes the largest unionist party at the Westminster parliament in London.
However, some believe the increase in DUP strength could benefit the peace process by making the party reluctant to face the electorate again should the review fail to find a formula for the Assembly's restoration.
Mr Donaldson walked out of negotiations shortly before the Good Friday Agreement was concluded in 1998 and he claims he voted `No' in the subsequent referendum.
He has generally opposed Mr David Trimble's policy ever since, but it took almost six years before the split became serious enough for Donaldson -- once considered a possible leader of the Ulster Unionists -- to resign from the party.