Stormont's ruling political parties have created a dangerous vacuum in Northern Ireland by failing to fulfil the promise of peace and reconciliation, the Fianna Fail leader has claimed.
A lack of commitment from the Irish and British governments to ensuring the power-sharing institutions north of the border work properly has also threatened hard-won gains of the peace process, Micheal Martin warned.
Mr Martin used his party's annual 1916 Easter Rising commemoration to reiterate his critical appraisal of the Democratic Unionist and Sinn Fein-led Executive and the supporting role of the Dublin and London administrations.
"In the Executive, Sinn Fein and DUP ministers show no interest in using their strength to bridge differences - in fact they do the exact opposite," he claimed. "More than at any stage since they took control of the Executive from the SDLP and UUP, they are adopting a strategy of playing to their own section of the community, even if this means attacking the very institutions they are supposed to oversee."
Mr Martin's vocal criticism of the Northern Ireland Executive has prompted accusations from political rivals that he is using the issue as a means to attack Fianna Fail's electoral competitors south of the border, particularly Sinn Fein and Fine Gael.
Addressing the Fianna Fail event at Arbour Hill cemetery in Dublin, Mr Martin claimed the DUP's stance in relation to parading and the loyalist Union flag protests and Sinn Fein's recent criticism of the Police Service of Northern Ireland were examples of failed leadership.
"What we are getting from these parties is what has rightly been termed all politics and no governance," he said.
"But what they don't seem to understand is that if the Assembly and Executive are not focused on the issues of concern to people every day like jobs and living standards - if all they do is reinforce suspicion, division and confrontation - then they are promoting disillusionment and failing to fulfil the promise of peace and reconciliation.
"As a party that claims to promote a Republican ethos, Sinn Fein is also letting down nationalist and republican voters in a very profound way. No number of half-baked border poll gimmicks should be allowed to distract from this basic fact. The DUP and Sinn Fein are creating a dangerous vacuum. We watched this year as the flags protests exploded on to the streets. All of us who care about the North should worry about what will move next to fill that vacuum.
"Fianna Fail will never back away from its commitment to active and constructive engagement between all parts of this island. We will never accept that the new dispensation so eagerly grasped by the people should be allowed to be undermined through a combination of neglect and partisan self-interest."