UUP decides to withdraw from Northern Ireland Executive
The Ulster Unionist Party (UUP) has confirmed that it will leave Northern Ireland's ruling executive.
Its ruling body voted unanimously in favour of a proposal by leader Mike Nesbitt for the party to pull out.
He had made the recommendation after police said members of the Provisional IRA were involved in murdering ex-IRA man Kevin McGuigan Sr.
Sinn Féin's denial that the IRA existed made it "impossible to do business with them," Mr Nesbitt said.
Danny Kennedy, the UUP's only executive minister, would tender his resignation on Tuesday, the party leader added.
And he described the executive as a "busted flush".
Chief Constable George Hamilton said in the wake of Mr McGuigan Sr's murder that an infrastructure still exists at a senior level of the Provisional IRA.
But he added there was no evidence that the killing was sanctioned by that hierarchy.
Sinn Féin said the Provisional IRA had "gone away" after ordering an end to its armed conflict in 2005.
Mr Nesbitt said the murder had been a "tipping point" for politics in Northern Ireland.
"[Sinn Féin's] position of denial over the existence of the IRA against the word of the chief constable makes it impossible to do business with them," he went on.
"We are walking out of the executive because we cannot sit with Sinn Féin because we do not trust them.
"The challenge at this tipping point is to fix what's wrong and to return to the vision of [the Good Friday Agreement in] 1998."
He said the party would now prepare to go into opposition in the Northern Ireland Assembly.
About 90 members of the UUP's executive met at a hotel in east Belfast to discuss Mr Nesbitt's recommendation for the party to pull out of government.
Analysis: BBC News NI political correspondent Stephen Walker
The DUP now has big decisions to make on whether to remain in the executive or follow the UUP and resign its ministerial positions.
That would bring power-sharing to an end and herald direct rule from Westminster for the first time since 2007.
Sinn Féin MLA Gerry Kelly said Mr Nesbitt had "abdicated his responsibilities" to the people who had voted for his party.
"I think [he] is setting leadership aside here for narrow party political reasons, even though he argues that it's quite the opposite," Mr Kelly said.
"This decision is based solely in attempting to gain an electoral advantage over the DUP and nothing else.
"What unionism needs to realise if it is pulling down these institutions is that they're not just punishing the nationalist vote, they are also punishing the voters who vote for unionists."
The DUP said earlier this week it believed that if anyone was excluded from government in Northern Ireland it should be Sinn Féin, "not unionists".
On Friday, DUP MP Sammy Wilson accused the Ulster Unionists of being opportunistic.
Traditional Unionist Voice leader Jim Allister said the UUP had "done the right thing", and urged the DUP to follow its move.
"It's no time for mere bluff and bluster, but it's time to face the reality that a Stormont executive built on the lies and excusing of IRA violence is a Stormont of not just failure, but shame," he said.
The SDLP and the Alliance Party both said ahead of the meeting that a decision by the UUP to leave the executive would be "premature".
Ivan Lewis, the shadow secretary of state for Northern Ireland, said the UUP's move left the political institutions "hanging by a thread once again".