The decision by Mr Jeffrey Donaldson's to leave the Ulster Unionist Party was a "mistake," according to a former Ulster Unionist colleague.
Mr David Burnside told the BBC's Inside Politicsprogramme today that he had attempted along with Mr Martin Smyth and Mr Jim Molyneaux to persuade Mr Donaldson not to leave.
He also expressed regret that two other assembly members, Ms Arlene Foster and Ms Norah Beare had decided to leave the party, a move he described as a "tactical mistake".
"I'm very sorry that Arlene has gone - she was a young officer with a great personality and a great future within unionism, in my opinion", said Mr Burnside.
Mr Donaldson and the two other assembly members left the UUP on Thursday. The Lagan Valley MP said he would negotiate with the DUP over Christmas and make an announcement on this future in the New Year.