The Northern Ireland Executive will meet only in “exceptional circumstances” amid an ongoing dispute between parties, the Democratic Unionist Party has announced.
Friction has developed between Sinn Féin and other parties after police said they believed IRA members were involved in the murder of Kevin McGuigan Sr.
McGuigan was a former member of the Provisional IRA, although Sinn Féin has rejected any link to the killing and insisted the IRA has “gone” and is “not coming back”.
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The row over McGuigan's killing – as well as ongoing disputes over welfare and budget cuts – prompted the Ulster Unionist part to pull out of the five-party executive last month to become an opposition party, a move that has raised concern over the future of the 1998 Belfast Agreement on power-sharing in Northern Ireland.
The Executive was due to meet on Monday, but first minister and DUP leader Peter Robinson said his party was not "prepared to continue as if nothing had happened".
"A man has been murdered at the hands of those linked to a party of government. This is unacceptable," he said.
"For our part we will take steps to ensure that pending a satisfactory resolution of the outstanding issues business will not be as usual."
Robinson said ministerial resignations could follow as a last resort to the crisis.
Sinn Féin has said it plans to continue working at Stormont despite the absence of other parties.
Northern Ireland Secretary Theresa Villiers will on Tuesday host talks at Stormont in a bid to resolve the crisis, with representatives from the DUP, Sinn Féin, the Ulster Unionist Party and the Irish government expected to attend.