The Clare TD Violet-Anne Wynne has left Sinn Féin, citing a lack of support at local party level.
Ms Wynne was first elected to the Dáil in February 2020.
In a statement to RTÉ News, she said that she believed that the administrative side of the party and organisers wanted her to stand down.
She claimed that the party had been "actively seeking this through gaslighting measures and what can only be described as psychological warfare".
Ms Wynne, a mother of six, gave birth to a baby girl last month.
However, she claims that her "unplanned pregnancy" had been used as a "further stick to beat me with", adding that she was concerned for women who may want to "come forward for Sinn Féin in the future, in Clare".
In a statement, Sinn Féin acknowledged "challenges" and "issues" at constituency level.
The Party's Deputy Chief Whip, Denise Mitchell said that she was "very sorry to hear of Violet-Anne's decision this morning", adding that the Clare TD was a "valued member of the Sinn Féin Oireachtas Team".
Ms Mitchell said that the party had "worked extremely hard over the past two years to resolve challenges at constituency level" and that those efforts would continue when Ms Wynne returned from maternity leave.
"Unfortunately, Violet-Anne has now decided to leave Sinn Féin. We wish her and her family the very best for the future", Ms Mitchell said.
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Ms Wynne felt that she hadn't been supported during her maternity leave.
She said that she requested an experienced office manager to assist her in her duties but instead was given "a prominent member of Sinn Féin" who was available for approximately three days a week.
Ms Wynne claimed that she was "pressured" into decisions that she couldn't stand over, such as the hiring of staff.
Sources at local party level say that they were surprised by Ms Wynne's announcement and were not expecting it.
The first time TD said that she was open with local party members about the "baggage" she carried prior to her election, explaining that she had "come from the dole to the Dáil."
However, she believed that this message was not passed onto the wider party as "I was told and treated as if I had blindsided the party".
She added that her decision to leave the party wasn't taken lightly.
Ms Wynne will continue to serve as an independent TD.
