Jim Gavin will be on the presidential election ballot paper when voting takes place on Friday 24 October and any votes cast for him will be treated in the same way as for the other two candidates, despite his withdrawal from the race.
On Sunday night, Mr Gavin announced he was withdrawing from the election "with immediate effect", after recent days had given him "cause to reflect".
It followed a report by the Irish Independent at the weekend that Mr Gavin owed a former tenant €3,300.
In a statement, Mr Gavin said he "made a mistake that was not in keeping with my character and the standards I set myself" and that he was "now taking steps to address the matter".
The Taoiseach said claims that Fianna Fáil knew about Mr Gavin's issue with a specific tenant before selecting him as the party’s presidential candidate were "not a fair representation of the situation at all".
Issue raised in 'generic and general way'
Speaking on his way into Government Buildings this morning, Micheal Martin said: "An issue was raised, but in a very generic and general way.
"We were not aware of any such issue, and that is the truth of it, and when the issue was raised repeatedly, we were told it was no issue."
Mr Martin said it was an "inaccurate construct to put on it" to state the party was aware of the issue earlier than when the tenant themselves "rang on Saturday".
Asked about Mr Gavin's name remaining on the presidential ballot paper, Mr Martin said: "That’s just the reality of how things have worked out. It’s very unfortunate."
The Fianna Fáil leader said the party had outlined all the reasons why Mr Gavin had to withdraw from the campaign.
Also speaking outside Government Buildings, the party's director of elections for the Presidential Election defended the vetting process carried out on Mr Gavin.
Jack Chambers said: "Fianna Fáil headquarters did a very comprehensive and robust due diligence process before his election as a candidate, any questions or queries that came to the party's press office were put to Jim Galvin, and he was absolutely clear on having no issues relating to a tenant.
"It's only what evolved over the weekend where obviously the difference of what was stated before and what emerged became absolutely clear. So there was absolute and full due diligence was done."
Talks with Attorney General
The Department of Housing and Local Government, which oversees electoral laws in Ireland, made the formal decision this morning after consultation with Attorney General Rossa Fanning throughout yesterday.
While the decision had been expected, it is understood that the department's Presidential Returning Officer Barry Ryan met the AG yesterday afternoon to discuss whether Mr Gavin will remain on the ballot paper or not.
Under existing electoral rules, although Mr Gavin has withdrawn from the campaign, his name cannot formally be removed from the ballot as he did so after the nomination process closed on Wednesday 24 September.
The discussions are understood to have involved a number of potential arguments surrounding this process, including whether the rarely used Section 164 of the 1992 Electoral Act could be used to remove Mr Gavin's name from ballots.
This section states that an "adaptation or modification where there is emergency or special difficulty" can take place in relation to a ballot in extremely rare circumstances.
Explainer: Gavin out of race but still on ballot paper
However, sources have noted that if such a rare step is taken it would potentially cause separate problems in relation to the first postal ballots which have already been sent out to students studying away from home, people unavoidably working abroad on voting day, and some people with disabilities.
In all, around 15,000 postal ballots are due to be distributed for the presidential campaign, with the concern being that if Mr Gavin was removed from the ballot then already sent postal ballots will have to be cancelled, returned and replaced as recipients would have a different name on the ballot to other voters - risking potential, if unlikely, legal cases.
As a result of these legal discussions, last night the Department of Housing confirmed in a statement that Mr Gavin must officially remain on the ballot.
This means that despite his withdrawal from campaigning, the former Dublin GAA manager will still be officially listed as a candidate that individuals can vote for if they so wish.
A vote for Mr Gavin on 24 October will not be counted as a spoilt vote, but will instead be counted as a vote for him, with any subsequent transfers of votes to other candidates also counted in the usual way.
If in the event Mr Gavin were to win the election despite having withdrawn from the race, he would be entitled to become president.
If he were to turn down that situation, the presidency would not go to the runner up candidate, but instead a new presidential election would be called.
Fianna Fáil said this morning that it first raised the issue of a possible dispute with a tenant on 8 September following a query from the Irish Independent.
But the party insisted that it was categorically assured by Mr Gavin on a number of occasions that there was no dispute with any tenant.
The party said this only changed on Saturday when Mr Gavin did begin to recall some details after the tenant had contacted Fianna Fáil with specifics.
Yesterday, Mr Martin said "very comprehensive due diligence" was done on Mr Gavin, but that an issue with a former tenant was "probably buried somewhere in the recesses of his mind".
Speaking on RTÉ's Six One News, the Taoiseach said Mr Gavin was "repeatedly asked" by the party if he ever had an issue with a tenant, which Mr Gavin had said: "Absolutely not."
"He clearly did not deal with it at that time or since, and probably buried it somewhere in the recesses of his mind and didn't deal with it and the consequences of that have now come home."
Watch: 'Very comprehensive due diligence' done on Gavin - Martin
Fianna Fáil MEP for Midlands North West Barry Cowen said a full and frank review of the process in selecting Mr Gavin as the party's presidential candidate needs to be carried out.
Speaking on RTÉ's Morning Ireland, Mr Cowen said he was not satisfied with the process that led up to the final decision and said there should be a more inclusive process that allows councillors and party members to engage fully in it.
Mr Cowen said he can understand why Mr Martin wanted to reach out beyond the party base in order to win the election.
However, he said, in doing so, he may have lost sight of the talent and experience already within Fianna Fáil, and the difficulties in motivating the grassroots to support someone the party was less familiar with.
Mr Cowen said he had supported Billy Kelleher in the nomination contest and that while Mr Gavin came highly recommended, he did not know him personally, but has worked closely with Mr Kelleher and knew his ability to engage with the public.
Mr Cowen said he respects Independent candidate Catherine Connolly, but he fundamentally disagrees with her on Ireland's place in the world and Europe.
I personally will be supporting [Fine Gael's] Heather Humphreys, he said.
