STORMONT has been plunged into fresh crisis after Sinn Fein dramatically withdrew support for welfare reform legislation just hours before a final vote on the bill.

The unexpected move has again cast a dark cloud of uncertainty over the power-sharing institutions – just months after the Stormont House Agreement was heralded as having delivered long-sought stability.

The shock development has triggered another bitter row between Sinn Fein and its main partners in the Executive – the Democratic Unionists – with both trading accusations of bad faith. 

The argument centres on the terms of Executive-funded mitigation schemes designed to support those benefit claimants set to lose out when the UK Government’s long-delayed welfare reforms are rolled out.

Announcing the change of stance, which ultimately prompted the vote on the Welfare Reform Bill to be postponed, Sinn Fein Deputy First Minister Martin McGuinness said: “The DUP have acted in bad faith and are now reneging on their commitments to protect the most vulnerable.”

The remarks drew an angry retort from DUP First Minister Peter Robinson.

“I have never seen such a dishonourable, ham-fisted statement as the one issued by Sinn Fein today,” he said.

Sinn Fein’s opponents have also questioned the timing of the announcement, coming as it did after the party’s all-Ireland Ard fheis (annual  conference) at the weekend, and have alleged a desire for power in the Republic of Ireland, where the party espouses a strident anti-austerity agenda in opposition, has influenced its balking at implementing cuts north of the border.

Consensus on introducing the welfare reforms, after a two-year impasse, was a key plank of December’s Stormont House Agreement between the five Executive parties and the British and Irish Governments.

Other elements of the deal, such as the devolution of corporation tax and a sustainable budget for 2015/16, are entirely dependent on the changes to the welfare system being introduced.

Legislation to enable the devolution of corporation tax powers has passed through Westminster, but the transfer of responsibilities is dependent on the Executive being on a firm financial footing.

With the Executive set to be hit with a £114 million bill from Treasury if welfare reforms are not implemented this coming financial year – having already been hit with £100m in penalties for the last two years – the consequences of not passing the legislation would be dire and would likely spell the collapse of the Executive.

Northern Ireland Secretary Theresa Villiers, who chaired last year’s Stormont House negotiations, said the developments were “deeply concerning”.

“I urge the Northern Ireland parties to work together to resolve this issue and continue the progress made so far in implementing the Stormont House Agreement,” she said.

“The Agreement offers us the prospects of stability, and of growing prosperity, building on corporation tax devolution. We must not put those prospects in peril. The situation requires everyone to show leadership and responsibility.”