Cork City councillor Lorna Bogue has resigned from the Green Party and said she has "little confidence" in the ability of its Cabinet ministers.
Ms Bogue, who opposed going into coalition with Fianna Fáil and Fine Gael, also cited the handling of the Mother and Baby Homes Bill.
In a statement, she said: "I did so because it became very clear to me that the leadership of the Green Party lacks the competence to make a substantive difference to the way that the Irish State treats its most mistreated groups as evinced by the handling of the Mother and Baby Homes Commission Bill."
She also said she had frequently cited the issue of misogyny in the Green Party but "active hostility" continued towards women.
Ms Bogue also ran for the party in the General Election in the Cork South Central constituency.
In a statement the party said: "The Green Party would like to thank Cllr Lorna Bogue for her tireless work with the party over the past years.
"The Green Party was saddened to receive Cllr Bogue's resignation and wishes her the very best with her work on climate and social justice at local and national level."
Earlier this year, another former election candidate, Saoirse McHugh, also resigned from the party.