Nine members of the Fine Gael frontbench have said they do not have confidence in Enda Kenny to lead their party.
Simon Coveney, Denis Naughten, Olwyn Enright, Olivia Mitchell, Fergus O'Dowd, Michael Creed, Billy Timmins, Leo Varadkar and Brian Hayes withdrew their support for Mr Kenny.
Spokesperson for the group Mr Naughten said frontbench members would like Mr Kenny to withdraw his motion of confidence and stand down in the interest of the party.
He said the leadership contest, which is now inevitable, will be extremely damaging for the party.
Mr Naughten said Mr Kenny had 'shut down' a meeting of the party's frontbench this morning.
He said the move had disappointed the group of TDs who had wanted to discuss the future of the party and his leadership with him.
Mr Naughten said he has privately had reservations over Mr Kenny's leadership for some time but has not publicly expressed them.
He said he and his colleagues had wanted to discuss those issues privately with Mr Kenny but that had not been possible.
Mr Naughten said the majority of the frontbench is not supportive of Mr Kenny's leadership and he said that it is his belief that situation is replicated within the wider parliamentary party.
Mr Naughten said it was extremely difficult for him to speak against Mr Kenny but he said he had no alternative given the way the situation has been handled by Mr Kenny.
Earlier, Mr Kenny said he will announce a major reshuffle of his party's frontbench next week.
Mr Kenny told his frontbench of the news at a meeting this morning, which followed the sacking of Richard Bruton as deputy leader yesterday.
His spokesman said Mr Kenny told a few 'home truths' to his colleagues about what had been going on over the last few months and with Mr Bruton over the last few days.
In a statement after the meeting, Mr Kenny said he looked forward to all 70 members of the parliamentary party having their say on Thursday.
Mr Kenny is said to have told his colleagues that it would be the parliamentary party, and not what he called a small group on the frontbench, who would decide the leadership of Fine Gael.
The party leader said there had been a failure of collective responsibility in recent months and suggested that over that period, Mr Bruton had not been as available to the media as he had been previously.
Before leaving, Mr Kenny told his colleagues this would be the last meeting of the current frontbench ahead of the reshuffle.
Speaking on RTÉ's Morning Ireland, Fine Gael Health Spokesperson Dr James Reilly said he is confident that Mr Kenny has a substantial majority of the parliamentary party.
He said Mr Kenny was a leader of great integrity, despite perceived problems about his ability to communicate.
Fine Gael Defence Spokesperson Jimmy Deenihan said the current difficulties are unprecedented and he was supporting Mr Kenny.
The leader of the Fine Gael delegation in the European Parliament has said the four Fine Gael MEPs would be backing Mr Kenny in Thursday's vote.
Gay Mitchell criticised some on the Fine Gael frontbench for the timing of the move against the party leader.
When asked to comment on Mr Bruton's actions, the Dublin MEP said the issue should not have raised its head at this time, adding that no one will thank Fine Gael for taking the heat off the Government when it is at 17% in the opinion polls.
He said the party needed the current unrest like 'a hole in the head'.
Mr Mitchell said that some in Fianna Fáil would be 'rubbing their hands and having great fun' and that some on the frontbench would have to ask themselves why they brought this about.
He said there was discontent within the party and said the issues would be dealt with.
However, he said that under Mr Kenny's leadership the party has more council seats than Labour and Fianna Fáil combined, and has more seats than any other Irish party in the European Parliament.
He also insisted that whoever wins the Fine Gael party leadership would be Taoiseach.