Taoiseach Enda Kenny has been left reeling by the Government's shock defeat in the referendum on the abolition of the Seanad.
The Taoiseach's position within Government and his own party has been significantly weakened by the result.
He warned: "Only half the party support Enda now.''
Several Fine Gael senators have also railed against the party's campaign strategy and were last night deeply critical of the leadership which oversaw the dramatic defeat.
Senator Catherine Noone said she was appalled by the tone and tenor of the party's "unreasoned" campaign.
She said: "Some of the personally insulting statements that came out of party HQ were very disparaging. One can only take such things personally.
"But there was also a lack of reasoned argument and I intend raising the matter next week. It was appalling."
Senator Tony Mulcahy was deeply critical of the party's use of "dubious figures" in relation to any potential savings that may be achieved by the Seanad's abolition.
"The €20m thing was a load of b******s. It didn't take a degree from Trinity College to do the maths," he said.
"This referendum is likely to cost €14m and paying us off would rack up another €6m. It's not rocket science," he said sharply.
He was also deeply critical of the running of so many "bull***t referendums" at a time when the Coalition should be concentrating on job creation. "The people are sick of this stuff. This was a total mess that they got themselves into," he added.
Senator Michael Darcy said he was appalled at the tone and tenor of the party's campaign and said he intends raising it when the party meets next Wednesday.
In contrast, a jubilant Niall Collins, director of elections for the victorious Fianna Fail 'No' campaign said the result was "a great day for democracy.''
The tide, he said, "began to turn once we got the debate on to an open pitch and were able to sweep away the spin and the populism''.
Mr Collins claimed the "voters had been turned off by the utterly disrespectful cynicism of a Taoiseach, who wanted to abolish the Seanad on a whim and then wouldn't debate the matter with the voters''.
He also said: "The Government is really going to have to learn – this is their second serious defeat on a major issue of reform. It shows how utterly they're detached from the people.'.
In another indication of widespread anger amongst the Fine Gael senators, Pat O'Neill, who is seen to be a close ally of Environment Minister, Phil Hogan, slammed a government campaign that is "too negative and too Americanised''.
Labour too was swiftly distancing itself from the Taoiseach's defeat.
One top level source noted: "This referendum was put on us by necessity.
"We agreed to put the proposition to the people and after that we made it very clear people were entitled to their own views."
The loss of the whip by Labour Senator James Heffernan, and the FG senators, Fidelma Healy Eames and Paul Bradford, means the Government, with 29 votes, does not have a majority in the Seanad for the first time since 1997.
Labour Senator John Whelan, said that whilst senators felt the referendum "was ill-considered and ill-thought", he believed the Government needs to run its full term.
Labour Senator Denis Landy also told the Sunday Independent: "We will look at every piece of legislation on a case by case basis.''
But laying down a significant marker, Mr Landy added that when it came to securing the support of government senators "we expect the Government to adhere to its election and manifesto promises''.
Meanwhile within Sinn Fein, division was also rife in the wake of a U-turn led by Deputy Pearse Doherty which saw the party end up on the wrong side of the referendum result.