Northern Ireland's power-sharing Executive has been plunged into fresh crisis after the Ulster Unionists announced their intent to walk away from the administration over claims the Provisional IRA still exists.
UUP leader Mike Nesbitt said trust in Sinn Fein had been shattered by the revelations and his party had been left with no option other than to resign from the five party coalition and form an opposition in the Stormont Assembly.
"Without trust there is nothing," Mr Nesbitt said.
While the dramatic move by one of the three minor coalition partners will not automatically trigger the collapse of the administration, it does throw its future into serious doubt, as pressure will now mount on the region's largest party, the Democratic Unionists, to follow suit.
If the DUP left the Executive it would fold immediately.
Sinn Fein accused the UUP of cynical politicking and claimed the party was trying to contrive a crisis to gain an electoral edge over the DUP ahead of next year's Assembly poll.
The UUP decision comes after the Police Service of Northern Ireland (PSNI) said structures of the PIRA are still operating, and some of its members were involved in the murder of Belfast father-of-nine Kevin McGuigan two weeks ago.
It is almost 20 years since the Provisional IRA's last ceasefire and a decade on from the supposed decommissioning of its weapons.
The UUP's one minister in an administration made up of 13 ministers and two junior ministers will resign next week if Mr Nesbitt's recommendation is supported by the party's ruling executive on Saturday - an endorsement that is widely expected.
Under the system used to allocate ministries, the DUP would take on the Regional Development brief vacated by the UUP's Danny Kennedy.
'This can be fixed'
An Ulster Unionist exit from the Executive would be highly symbolic given the party was one of the architects of the 1998 Good Friday peace agreement that paved the way for nationalists and unionists to share power. The accord did not envisage an Assembly with an official opposition.
Mr Nesbitt claimed Sinn Fein's continual denials about the IRA had punctured a hole in the fabric of the agreement.
"We are in a bad place, but this can be fixed," he said.
"But the IRA need to go away and stop terrorising their own communities.
"So do the UDA, and UVF and Red Hand Commando - and the rest.
"And I wouldn't argue if they took down their paramilitary flags on the way out.
"Our vision remains that of a Northern Ireland that is totally peaceful and where everyone prospers - republicans, nationalists and unionists equally."
Sinn Fein Deputy First Minister Martin McGuinness accused the UUP of playing party politics.
He said on Twitter: "This decision by the UUP is more about inter Unionist rivalry than their & others feigned concern about our unequivocal commitment to #Peace."
At the weekend, PSNI chief constable George Hamilton said that the IRA still exists but is not engaged in terrorism, instead pursuing peaceful, political republicanism.
However, the PSNI also said some PIRA members were involved in the murder of former IRA man Mr McGuigan, 53, in co-operation with a group styling itself Action Against Drugs. Detectives said there is no evidence the killing was sanctioned by the IRA leadership.
Mr McGuigan was suspected by some in the republican movement of involvement in the murder of former IRA leader Gerard "Jock" Davison in the nearby Markets area of Belfast three months ago.
Police believe his killing was a revenge attack by Mr Davison's republican associates.