A councillor who quit the Green Party to join the SDLP had just weeks earlier been considering a switch to Alliance.
Simon Lee is understood to have made an approach to Alliance within days of May's Stormont election, in which he ran unsuccessfully as a Lagan Valley candidate for the Greens.
Further discussions were held but the Lisburn and Castlereagh councillor some weeks ago decided against joining Naomi Long's party.
