Peadar Tóibín is to travel around the country to establish an alternative political organisation after resigning from Sinn Féin after 21 years in the party.
The Meath West TD had been on a six-month suspension from the party after he voted against legislation to allow for the introduction of abortion services in this country.
In his letter of resignation Mr Tóibín, a strong pro-life advocate, said he had not received a response to an email in which he asked if there was "a future" for him or other members who are against the rollout of termination services.
Speaking after his resignation, Mr Tóibín said: "I have been getting a lot of contacts from people from a Fianna Fáil background, from a Sinn Féin background who are really frustrated with regards the direction the leaderships are going and the lack of space for different views.
"So over the next month it is my objective to go around the country to meet people who have similar views as myself from different political backgrounds and see if we can fold those people into a tight organisation that can actually represent those views and work hard for those objectives of a united Ireland and economic justice for people."
Reacting to the resignation, Sinn Féin president, Mary Lou McDonald, said her party is a "home to a diversity of views".
"Unfortunately, Peadar was unable to do this and was suspended from the party and has now taken the decision to resign. I wish Peadar and his family well for the future," she said.
But Mr Tóibín said there "are clear problems in the organisation and those clear problems need to be resolved" adding "if they don't fix them, I won't be the last" to step down.
He ruled out ever returning to Sinn Féin.