An outspoken Fine Gael rebel who quit the party has accused the leadership of gunning for him.
Former banker consultant Peter Mathews said senior figures had taken "deconstructive" and "destructive" moves against him after his rebellion over landmark abortion legislation.
"My basis of joining the party included the right to vote in accordance with my conscience on certain important matters, vital matters, to do with life and death and certain constitutional matters," Mr Mathews said.
"It came as a surprise that that part of my contract of joining the party and going forward as a candidate was overlooked completely."
The TD for the Dublin South constituency, who only joined the party one month before the 2011 general election, claimed he was forced into his decision to quit.
Following his expulsion from the Fine Gael parliamentary party in the summer, Mr Mathews was removed from two Oireachtas committees - the finance public expenditure and public policy oversight petitions - in which he claimed he had made some "meaningful and strong contributions".
"They were deconstructive, if not destructive, moves," Mr Mathews said.
"I just felt this was a bit meaningless, very unnecessary."
He added: "So really, the leadership has created a position for me that has led me to this decision and it has all happened in a gradual and in a carefully and thought about way."
Mr Mathews, who lost the party whip after he voted against the Protection of Life During Pregnancy Act, said he would stand for the Dail a second time at the next election.
He said he had been told by the Fine Gael leadership that there was no way back for him.
Mr Mathews sent a text to Taoiseach Enda Kenny on Wednesday night, announcing his resignation.
He said he would work on as an Independent and would consider contributing to and sharing ideas with the Reform Alliance - a group made up of former Fine Gael TDs and Senators who voted against the Government on the abortion legislation.
Among them is Lucinda Creighton, Billy Timmins, Terence Flanagan and Denis Naughten, along with senators Paul Bradford and Fidelma Healy-Eames.
Mr Mathews added that he had no intention of trying to score points against any political party.
He urged all groups in the Dail to "shake down and become a bit more match-fit", and to combine their resources.
The banking expert joined Fine Gael in 2011. He succeeded journalist George Lee who, like him, was parachuted into the Dublin South seat by the party.
Mr Lee quit after only nine months in the Dail - claiming he realised he could make no real difference in shaping Fine Gael policy.
Both men had carved out high profiles within the media across TV and radio.