A Sinn Fein councillor has quit the party, claiming she has experienced bullying, hostility and aggression.
The resignation of Sorcha O'Neill, a representative for Naas, Co Kildare, has sent shock waves through the organisation following accusations that her complaints were ignored by the party hierarchy.
Five other party activists in the Kildare area have also quit.
"When you have members coming to you saying they're losing sleep and are distraught, we came to a decision that it was just best to leave the party because it was so unhealthy," Ms O'Neill said.
It is the latest in a series of controversies to result in members leaving the party.
In Cork, two councillors have resigned, along with former TD Sandra McLellan who alleged she was bullied out of her position by party colleagues.
Sources said the new row involving Ms O'Neill was linked to unelected representatives asserting substantial influence on local decisions.
Ms O'Neill, who attracted 1,622 first-preference votes in 2014, told Kildare FM that she felt "intimidated" and that people had suggested her work ethic was "less than desirable".
"There's not one thing. It's a culture that has come up and it's not something that you can talk out of," she said.
"These are personalities that don't see anything wrong in what they're doing. I have myself tried to reason with certain members."
Ms O'Neill said she raised "multiple concerns" with Sinn Fein's head office over recent years but failed to get any more than a "casual response".
"I would have hoped something more solid would have come out of it," she said.
A spokesperson for Sinn Fein said Ms O'Neill's statement had "come as a surprise" to them. The party said she should "reflect on her position".
"She was a dedicated and capable member of our team and on the council," the spokesperson said.
"If there are issues in the constituency we will look at them, but Sorcha is a valued member of Sinn Fein and we would hope she will reconsider her position.
"We acknowledge that there are difficulties present in the area which we are working to address."
The statement concluded by wishing Ms O'Neill the best in the future.
Sinn Fein has also had problems in Wicklow, where councillors have rowed over who should be the local group leader.
Three councillors were stripped of the party whip after failing to support councillor Michael O'Connor's nomination for chairman of Wicklow County Council and Nicola Lawless as deputy chairperson.
Councillors John Snell, Gerry O'Neill and Oliver O'Brien are seeking a full hearing involving the party's ruling body, the Ard Chomhairle. They are unhappy with the manner in which councillor Lawless was appointed.