Fianna Fáil has received a letter of resignation from former minister and EU Commissioner Pádraig Flynn.
Party leader Micheál Martin was due to propose a motion to expel him from the party at Friday's Ard Chomhairle on foot of the findings of the Mahon Tribunal.
Fianna Fáil also received correspondence from Bertie Ahern this morning - confirming his decision to resign from the party.
On Friday, the Fianna Fáil national executive will consider motions calling for the expulsion of one serving and three former councillors.
Earlier, Fianna Fáil TD Éamon Ó Cuív said he could not understand why people were not formally charged with crimes if they were seen to be breaking the law.
Mr Ó Cuív was speaking on Raidió na Gaeltachta's Iris Aniar this morning in relation to the Mahon Report.
He said that files that related to law-breaking should have been given by the Mahon Tribunal to the Director of Public Prosecutions or to the gardaí up to 15 years ago.
Mr Ó Cuív said criminal proceedings should have been put in place at that stage and said such an issue would not arise in other countries.
The former minister also said that he did not see any issue arising from the report that would bring Micheál Martin's leadership of Fianna Fáil into question.
This morning, a Fianna Fáil vice president described Bertie Ahern's announcement as a "token effort".
Speaking on RTÉ's Morning Ireland, Lisa Chambers said she did not accept the former Taoiseach's denials of the findings of the Mahon Tribunal.
"I believe that he already knows what's about to come and he’s trying to, in a sense, beat us to it," she said.
Fianna Fáil Justice spokesman Dara Calleary said the agenda of Friday's meeting will be unaffected by today's announcements.
A vote on expelling Mr Ahern from Fianna Fáil will not now be held, but a recommendation that there should be a root and branch review of the organisation in Dublin Central, Mr Ahern's constituency, will be tabled.
Mr Calleary told RTÉ News that the fallout from the Mahon Tribunal report would still be considered.
In an article in today's Irish Times, Mr Ahern said resigning from Fianna Fáil had been a "real emotional wrench" because the party had been an integral part of his life for 40 years.
He reiterated his contention, made in yesterday's Sunday Independent, that he never took a corrupt payment and that he told the Mahon Tribunal the truth.
Mr Ahern stressed that his decision to resign was a political decision, and not in any way an admission of wrongdoing.
He also said he appreciated the gestures of all those who had contacted him to wish him well.