Update 14.11pm Peadar Tóibín says a number of Fianna Fáil TDs are potentially interested in joining a new political party he is hoping to set up.
The Meath West TD has decided to resign from Sinn Féin as he felt he was repeatedly marginalised by the party for his anti-abortion views.
He was suspended from Sinn Féin earlier this month for ignoring the party whip and voting against the abortion legislation.
Deputy Tóibín says a number of TDs want a new platform.
He said: "A lot of people from Fianna Fáil, believe it or not, over the last month or two are absolutely frustrated with Micheál Martin's - what they called two fingers to the membership on so many different issues.
"Those individuals are desperately crying out for some kind of platform to allow them work for the objectives that they have.
Sinn Féin Mary Lou McDonald leader has expressed regret at Peadar Tóibín's decision to resign.
Ms McDonald says there is a responsibility on all Sinn Féin TDs to represent party policy, which Deputy Tóibín was unable to do.
- Digital Desk
By Elaine Loughlin
Peadar Tóibín has resigned 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 abortions 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 of the party who are against the rollout of termination services.
He said he was leaving Sinn Fein with "a heavy heart" as he had poured all his efforts into the goals of achieving Irish unity and economic justice.
"This clearly is no longer enough," he wrote.
It is with a heavy heart that I resign from Sinn Féin today. I have been a member of the party for 21 years. In that time I poured all my efforts into achieving Irish Unity & Economic Justice. This clearly is no longer enough. I will now help to build a new 32 County movement. pic.twitter.com/RqzimdR8Zp— Peadar Tóibín (@Toibin1) November 15, 2018
Writing to Sinn Fein party whip Aengus Ó Snodaigh, Mr Toibín said: "Over two weeks ago I wrote an email to the Cathaoirleach of the party. I also CC'd it to the leader and to yourself.
"The letter sought to find out was there a future for me and republicans like me to contribute to the development of the party in a fair and equal manner.