The leader of the DUP used the party’s spring conference to savage Sinn Fein for its decision to walk away from the welfare deal it had agreed.
Peter Robinson told delegates at the weekend it was “inconceivable” that his republican power-sharing partners had not known what they were signing up to when they originally agreed the deal.
He also used the address to defend the creation of a polling day pact with unionist rivals, which has seen the DUP and UUP field agreed candidates in four seats – saying that the very fact it was being attacked showed it was valuable.
Sinn Fein, for its part, dismissed the speech as “pre-election bluster”.
Speaking of the moment that a deal was finally struck on bringing in changes to the welfare system, Mr Robinson said: “This was a massive breakthrough that resolved outstanding issues and created the potential for long-term financial stability and prosperity.
“Delivery remained on track right up to a few weeks ago when, out of the blue, we were asked to believe that someone turned the lights on in Connolly House and Sinn Fein suddenly realised that what they had negotiated and agreed was not what they thought they had signed up to.
“This represented either an alarming act of bad faith by Sinn Fein or the most inept negotiating by republicans in the history of the process.
“For myself I find it inconceivable that they did not know or understand what was written and detailed in the document agreed by them at Stormont.”
The disagreement centred on a fund which would make up the difference for any families which lost out on cash under the new welfare system agreed by the deal.
However, Sinn Fein had claimed, weeks after backing it, that this fund did not go as far as the party had wanted.
Mr Robinson said: “Given the sums of money involved – no one with post-primary education could possibly have believed that the funding envelope in the agreement could have covered the entirety of the shortfall for each and every claimant now and in the future.
“I make some allowance for Sinn Fein’s poor grasp of economics but not even they could have thought a fund of £20m per year could have covered what they once claimed to be a gap of £450m.”
Sinn Fein hit back: “We have consistently and publicly declared our determination to protect children and adults with disabilities, the long-term sick and families with children against Tory cuts.
“That was our position before, during and since the Stormont House Agreement. That remains our position.
“There will be no progress on any other basis. These are red-line issues for Sinn Fein.”
On the electoral pact, which will see agreed candidates run in Fermanagh and South Tyrone, Newry and Armagh, East Belfast, and North Belfast, Mr Robinson said he had been “delighted” to unveil the agreement, adding: “And it’s working. How do I know? I know it’s working because our political opponents are snorting and ranting – they don’t like it.
“I can’t think of anything that antagonises the enemies of unionism more than the idea of unionists working together.”
He added that he had wanted Upper Bann and South Belfast included too, and told delegates that only the DUP could deliver a unionist victory in these areas.
Mr Robinson also used his spring conference speech to outline the five main, broad areas which the party would prioritise – the first of which was the economy:
• Make Northern Ireland an economic powerhouse
• Deliver world class public services for our people
• Create a society based on fairness and opportunity for everyone
• Make politics and government work better in Northern Ireland
• Strengthen the United Kingdom and protect and enhance our British identity.