The Social Democrats has confirmed that party chair Glenna Lynch has resigned from the party.
A spokeswoman from the party said that Ms Lynch had indicated she did not feel she was in a position to participate fully any longer.
She had already indicated she would not be running as a candidate for the party.
Ms Lynch, a businesswoman, came to national prominence when she challenged the Independent candidate Sean Gallagher on his business record in a live televised debate ahead of the 2011 Presidential election.
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Ms Lynch was not contactable for comment on Sunday.
