The vice-chairman of the SDLP Eddie Espie quit the party this evening claiming it was a shadow of the organisation he joined.
Mr Espie, who has been the SDLP's vice chair since February 2004, launched an angry broadside at the party leadership, accusing it of failing to listen to the rank-and-file's calls for reform.
And he also claimed the party would struggle to re-elect its current total of 18 Assembly members. His accusations, however, were challenged by a party spokesperson who expressed regret at his decision to stand down.
Mr Espie said what little strategic direction there was in the party appeared to come from a tiny unrepresentative elite which was more concerned with the current political situation rather than with any long-term electoral strategy.
"At the centre of the SDLP's difficulties is the detachment between the ordinary membership on the ground and political leadership," he said.
"This interaction function should be at the public face and at the hub of everything the SDLP does.
"Strategy is acceptable but unless it is received and understood by the proper audiences, it changes nobody.
"The existing situation where some senior staff at headquarters, in collaboration with cabals who run the party, disregard the opinions and needs of grassroots members is indefensible.
"Common courtesy costs nothing but means a lot to these dedicated members across the North.
"The party team at all levels, needs to be unified, cohesive and consistent, with a clear plan for the present and for the future. Noticeably, this is not presently the case."
Mr Espie also accused the leadership of failing to connect with a large proportion of nationalists in Northern Ireland who would never and could never vote for Sinn Fein.
"The SDLP ought to be perfectly positioned to secure the votes of these people, but unless the overhaul begins with immediate effect this opportunity will be lost," he warned.
"This unpalatable reality is being ignored and while it is being ignored, the downfall will continue unabated.
An SDLP spokesperson said the party regretted Mr Espie had chosen to resign. He added: "The SDLP has embarked on a process of change, restructuring and renewal over the last 18 months. That process will continue."