Peter Robinson and Martin McGuinness have clashed in public for the first time, as the split at the heart of the power-sharing government was dramatically exposed.
As the pair appeared before the cameras at a press conference after a north-south ministerial council meeting in Limavady on Monday, Mr McGuinness accused his counterpart of raising roadblocks to a deal.
Read Ken Reid's blog: Double trouble
As the men stood side-by-side in front of the media, a visibly angry Mr Robinson effectively reprimanded his opposite number accusing him of bringing private details into the public domain.
Mr McGuinness continually shook his head in disagreement as Mr Robinson spoke.
'Crisis'
UTV's Political Editor Ken Reid said the exchanges were seen as a public demonstration of the two leaders' long-running private dispute.
"It doesn't look to me as if there will be a date before Christmas. That means after the holiday and into the New Year the governments will intensify their efforts to try and get this matter sorted.
"There have been suggestions that Sinn Fein could walk away from the institutions - but I'm told that's not likely to happen before the Assembly resumes on 11 January. But I think if there's no progress at that point then we are facing a full-blown crisis," Ken Reid said.
The Sinn Fein leader hit out at DUP calls for a scrapping of the Parades Commission, which rules on Orange Order parades, and said it could not be a pre-condition to a deal on the transfer of policing and justice powers.
Mr McGuinness: "I move forward against the backdrop of the agreements that I made with Peter Robinson 13 months ago where we agreed an over-30 step approach to the transfer of powers on policing and justice.
"I have to say at no stage in that process was the issue of issues being used as pre-conditions for the transfer of power for policing and justice mentioned."
In a reference to a DUP letter to the Prime Minister demanding 'confidence building' measures for unionists before a deal, Mr McGuinness added: "At no stage were people contemplating sending, on solo runs, letters to Prime Ministers which effectively I had not seen, was not made aware of and was completely surprised by."
Mr Robinson hit back by claiming republicans had already backed reform of parades, but had now opted to delay the measures as a tactic.
The First Minister, who glanced at his adviser and became visibly angry as Mr McGuinness spoke, added: "I regret the tone of the latter remarks.
"I don't think that it is helpful for us to be going into the finer details of these matters, but nobody is in any doubt that the issue of parades was moving forward and was held back."
The clash came as Irish Taoiseach Brian Cowen led a team of his government's ministers in a session of cross-border talks with members of the Stormont administration.
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