FIANNA Fail TD Eamon O Cuiv is to make a statement this evening about whether he will leave the party founded by his grandfather Eamon de Valera, as months of conflict with leader Micheal Martin finally come to a head.
Mr O Cuiv has already been stripped of the deputy leadership as well as a position on the frontbench over his stance on the fiscal treaty.
He said today that he would issue a statement after 5pm about his future intentions.
The Galway West TD is advocating a No vote, while Mr Martin and the rest of the parliamentary party is campaigning for a Yes.
Speaking to the Irish Independent, Mr O Cuiv said: "I have two choices -- leave the party or say nothing about the treaty."
He said it was fairly clear to him he would have to leave the party if he campaigned or spoke in the media in favour of a No vote in the referendum. He also insisted his grandfather and family heritage would have no bearing on his decision.
"It's a fairly stark decision that I have to take," he said.
He claimed he was sent a letter by party chief whip Sean O Fearghail outlining Fianna Fail rules and its stance on the treaty.
He also claimed it was clear "they" wanted him to leave the party. Mr O Cuiv said he will make a final decision this evening, insisting he will not join Sinn Fein if he leaves but will become an Independent.
Last night, Fianna Fail rejected rumours that Mr O Cuiv has already resigned -- and that he had done so at a party meeting in Galway.
Mr O Cuiv has become increasingly rebellious in recent weeks, criticising Mr Martin for being too much of a Europhile and then suggesting Fianna Fail could join with Sinn Fein.
It is understood he had come to an arrangement with Mr O Fearghail that allowed him to go against the treaty but barred him from actively campaigning.
His decision tonight will be on whether to leave the party entirely and not just lose the party whip in the Dail.
His approach in recent weeks has angered other TDs, who feel he is trying to "martyr" himself.
Differences emerged between Mr O Cuiv and Mr O Fearghail last night, with the whip claiming the former deputy leader insisted the party write him a letter over the weekend.
The pair held meetings on Friday and Saturday, and Mr O Fearghail insisted the letter did not contain any reference to leaving or getting kicked out of Fianna Fail.
"I had no idea he was thinking this way. He hadn't suggested to me that he would do anything like this," he added.