The future of Northern Ireland's power-sharing administration is in question after bitter exchanges between Sinn Féin and the DUP and the withdrawal of a Welfare Reform Bill.
Sinn Féin pulled its support for welfare reform legislation in Northern Ireland.
However, both parties have accused each other of bad faith.
In a statement, Minister for Foreign Affairs Charlie Flanagan called the developments "deeply disappointing."
He said: "While the content of this Bill is primarily a matter for the parties in the Northern Ireland Executive and the British Government, an agreed way forward on welfare was a key component of the Stormont House Agreement.
"Failure to implement this aspect could have a corrosive impact on the wider implementation of the Agreement.
"Accordingly, I call on the Northern Ireland parties, and in particular Sinn Féin and the DUP, to avail of the time and space provided by the deferral of the Bill to work together to find a solution to the current difficulties on welfare.
“Such a solution can only be found by patient and mutually respectful dialogue."
A resolution of the impasse over the non-implementation of the UK government's welfare reforms in the region was a key plank of December's Stormont House political agreement.
Sinn Féin had supported the legislation through the Assembly since.
However, ahead of today's final stage in the chamber, the party reversed its stance, accusing the DUP of acting in bad faith.
The Stormont House Agreement essentially paved the way for the implementation of the government's welfare reforms alongside a series of Stormont-funded packages to support those whose benefits were set to be cut.
Sinn Féin Deputy First Minister Martin McGuinness accused the DUP of reneging on commitments he said had been made in the Stormont House deal.
"At Stormont House the five parties agreed a series of measures to protect the vulnerable and safeguard current and future welfare claimants under the control of the executive," he said.
"However, the DUP have acted in bad faith and are now reneging on their commitments to protect the most vulnerable."
The introduction of welfare reforms in Northern Ireland have been delayed by over two years, primarily due to Sinn Féin's reluctance to sign up to measures it claimed would hit the most vulnerable.
The row appeared to have been sorted in December's Stormont House political deal when the five executive parties agreed to offer additional financial assistance to claimants from its own pockets.
Northern Ireland's leaders had warned that the very future of the power-sharing executive would have been under threat had the agreement not been reached - as multi-million pound Treasury penalties for non-implementation would have been too much to shoulder.
Sinn Féin's announcement casts doubt over the progress supposedly achieved in December.
