Days after exchanging angry accusations over the stalled introduction of a revised welfare system, DUP First Minister Peter Robinson and Sinn Féin Deputy First Minister Martin McGuinness have surprised many by appearing side by side outside Stormont Castle to report a degree of progress.

The significantly more upbeat assessment came after an apparent breakthrough was made during five hours of intensive discussions and number crunching between DUP and Sinn Féin delegations.

“We have had discussions which I think were useful during the course of today,” said Mr Robinson. “It is our intention to give work to officials to carry out over the next couple of hours and it is not without hope that we can reach a resolution on the issue, but there is still a long way to go.”

Mr McGuinness added: “Further work has been taken forward which I think leaves us very hopeful about the future in terms of overcoming the difficulties facing us at the moment.”

The row flared on Monday after Sinn Féin’s shock decision to withdraw support from welfare legislation just hours before a final Assembly debate.

Implementing the Government’s changes to the benefits system is a key plank of December’s landmark Stormont House Agreement and, without passing the already long-delayed legislation, the whole deal would likely implode.

The latest wrangle centres on whether Stormont-funded mitigation schemes designed to support those in Northern Ireland who would lose out under the reformed UK welfare system will cover future claimants, not just existing ones.

Sinn Féin pulled support after alleging the DUP had acted in bad faith by proposing to limit the schemes to current claimants.

The DUP has insisted there had never been an agreement to support future claimants and said such a system would require another £286 million.

Mr Robinson and Mr McGuinness were at Stormont Castle to brief the leaders of the Executive’s three smaller parties on the outcome of Friday’s negotiations.

Talks broke up after half an hour with the party representatives due to meet again at the start of next week to examine the figures worked up over the weekend by Stormont officials.

The devolution of corporation tax powers to Belfast and new mechanisms to address the legacy of the Troubles would be in jeopardy if the Stormont House deal collapsed, while the Executive would unlikely be able to balance its books in the next financial year.

With the British government insisting no money is on offer from the Treasury to resolve the problem, the impasse has to be sorted between the five local parties.

Friday’s negotiations took place as a mass strike by public sector health, education, civil service and transport staff against spending cuts envisaged in the Stormont House Agreement was staged across Northern Ireland.

After the half hour meeting, the SDLP's Alban Maginness said he would reserve judgement until the final figures were presented.

“We’ve heard things like this before and we will judge this when we have a definite result,” he said. “We are awaiting financial papers in relation to the whole issue and we will be able to study the situation carefully then.

“We reserve a degree of scepticism and that is proven by the way things have happened here and of course a lot of the problems that arise here arise because you have two parties dealing with one another, rather than dealing with everybody else.”

Ulster Unionist leader Mike Nesbitt said an "excellent official" in the Department of Social Development should be credited for the progress.

“It appears the DUP and Sinn Féin have made some progress thanks to one of the most excellent civil servants who you will ever come across in Social Development,” he said. “He has taken the matters away. He is going to need a couple of days to work up the detail of a solution – the solution seems to be there.

“The lesson of it is to the political parties, and particularly Sinn Féin – if you don’t pay attention as you negotiate then these issues come back to bite us afterwards and bring all of us into disrepute in the public domain.”

Ahead of the meeting, Alliance party's Employment and Learning Minister Stephen Farry said there was an urgent need for a settlement.

“If we don’t sort this out there is a very real danger of an awful lot of things unravelling,” he said. “We’ll see Northern Ireland’s credibility as an investment location damaged because good governance and the ability to follow-through on decisions lies at the heart of good government, so our reputation both as a country and as a society is at stake.”