However, party sources last night said Mr Ó Cuív, the grandson of Eamon de Valera, was free to say what he wanted and that the Galway TD was unlikely to face disciplinary procedures.
The comments came after another poor opinion poll for Fianna Fáil and after one senator last week quit the parliamentary party in disagreement over its stance on same-sex couples parenting.
The party is facing internal criticism from its own TDs, with one high-profile member yesterday suggesting its fight as a party was fading.
Mr Ó Cuív, whose grandfather founded Fianna Fáil, told the Sunday Independent: “There was more fight in Fianna Fáil in 2011 and 2012 than there is today. A great lassitude has spread across the party from top to bottom. There has been an absolute collapse in self-belief. We are becalmed. If all you see in Fianna Fáil is nostalgia and lethargy it will very quickly be all over for Fianna Fáil. If our party membership thinks our future is as a new SDLP, they will fade away very quickly.
“There is a difference between the top of Fianna Fáil and the supporters that is utterly corrosive.”
Mr Ó Cuív has made known his criticism about the direction Fianna Fáil is going previously and has even hinted a future coalition with Sinn Féin should be considered.
He said the party was facing “demise”.
His latest comments will raise more questions about party leader Micheál Martin and whether he has the ability to bring his TDs and senators with him through to the next general election.
A Red C poll at the week- end also showed Fianna Fáil plateauing on 18% since the last poll.
The party also lost one parliamentary member last week after senator Jim Walsh resigned the whip over his stance on gay people using assisted reproduction under new family legislation.
A party spokesman last night said Mr Ó Cuív’s remarks would be dealt with internally and that no comment was being made.
Some sources though also said: “There’s no disciplinary process here. He’s entitled to say what he thinks.”
Party figures have privately warned a heave may be brought against Mr Martin if Fianna Fáil fails to win a seat in May’s Carlow-Kilkenny byelection.
Meanwhile, the party last night held its biggest selection convention for general election candidates, with 1,500 delegates voting on who will represent it in Kerry.