Martin Morgan, a leading member of the nationalist SDLP and a former mayor of Belfast, is to leave politics.
Mr Morgan told his party of the decision some weeks ago but it only became public this week.
A member of Belfast City Council for north Belfast for the past 12 years, Mr Morgan was seen as carrying the torch for a new generation in a party which has struggled to cope with the retirement of the party’s leading lights, John Hume and Seamus Mallon.
Mr Morgan almost uniquely bore the stamp of an SDLP activist, rather than an career politician.
Mr Morgan is understood to want to devote more time to his career as a social worker.
Local government elections are scheduled for next year and he will not defend his council seat. Mr Mark Durkan, the SDLP leader, said Mr Morgan was “a loss to frontline politics”.
His withdrawal from pòlitics will be seen as a possible nail in the coffin of Sinn Féin’s nationalist competition, which is facing the loss of all its seats in the next election to the Westminster parliament in London.