The Fianna Fáil TD Eamon Ó Cuív has said he will announce this afternoon whether or not he has decided to leave the party.
It follows a letter from the party whip over the weekend asking him to refrain from media interviews campaigning for a 'No' vote in the Fiscal Treaty referendum.
The former Minister said he has a monumental decision to make today about whether to remain in Fianna Fáil or not.
All other Fianna Fáil TDs and Senators have agreed to campaign for a 'Yes' vote in the referendum.
The letter sent to Mr Ó'Cuív featured reminders about a pledge signed by TDs to adhere to party policy.