Stormont crisis: How the story unfolded

Stormont's political crisis was sparked by allegations Provisional IRA members were involved in the murder, in August, of Belfast man Kevin McGuigan Sr.

A row erupted after a senior Sinn Féin member was arrested as part of the inquiry into Mr McGuigan's death. He was later released without charge.

The crisis deepened when Northern Ireland First Minister Peter Robinson stepped aside on 10 September, along with all but one of the ministers from his Democratic Unionist Party (DUP).

Mr Robinson's announcement came after the DUP failed to get the assembly adjourned for talks to address the situation.

DUP ministers then resigned and were reappointed more than 20 times.

They resigned on a weekly basis and were reinstated in order to prevent other parties claiming the vacant seats.

Other parties criticised the DUP's "in-out" approach to devolution. The DUP ministers resumed their posts on 20 October.

Why is the stability of the Northern Ireland devolved government under threat?

Kevin McGuigan Sr was murdered in a gun attack in east Belfast in August

For months the power-sharing executive at Stormont has been deadlocked over budgetary matters.

Underlying this disagreement was Sinn Féin's refusal to implement welfare reforms introduced elsewhere in the UK.

However, the political crisis deepened in August after the police said current IRA members may have been involved in Kevin McGuigan Sr's murder.

He was a former member of the Provisional IRA and according to police, one of a number of suspects in the murder of Gerard Jock Davison, who was shot dead in May.

Unionists argued that if the IRA remains active, Sinn Féin should be excluded from ministerial office.

What action did the DUP take?

DUP leader Mr Robinson stepped aside as first minister and three other DUP ministers resigned in protest over allegations that the IRA still exists and its members were involved in Mr McGuigan's murder.

Mr Robinson asked his party colleague Arlene Foster to take over as acting first minister and remain in her current post of finance minister.

He said this was "to ensure that nationalists and republicans are not able to take financial and other decisions that may be detrimental to Northern Ireland".

He also called an end to meetings of the Stormont Executive in September and said there would be no formal meetings between Northern Ireland ministers and their counterparts from the Republic of Ireland.

The assembly's business committee voted against adjournment.

Mr Robinson could ensure the executive did not meet, because it must be convened jointly by him and Sinn Féin Deputy First Minister Martin McGuinness.

Mr Robinson resumed as first minister on 20 October.

Why did the DUP ministers resign?

DUP leader Peter Robinson stepped aside as first minister as tensions grew

The DUP initially wanted Sinn Féin excluded from ministerial office, but such a proposal would be defeated in the Stormont Assembly because it would require cross-community support.

The second largest unionist party in Northern Ireland, the Ulster Unionists, turned up the pressure on the DUP by withdrawing their only minister from the power-sharing executive.

The DUP asked Prime Minister David Cameron to suspend the Northern Ireland Assembly, but following the DUP resignations, Mr Cameron's spokesperson said "the UK government did not believe it would be right to introduce emergency legislation now to suspend the assembly".

Have Northern Ireland Executive meetings been disrupted in this way before?

The power-sharing executive, which brings together all 15 Stormont ministers, normally meets every two weeks.

In 2008, Sinn Féin declined to convene a meeting of the executive for five months, because the party was frustrated about delays over the planned transfer of justice powers to the devolved government. The dispute was resolved in cross-party talks.

What happened after the DUP ministers resigned?

Arlene Foster became acting first minister in the Northern Ireland Assembly

The Northern Ireland Executive could not survive the resignation of all its unionist ministers - but that did not happen.

Instead Finance Minister Arlene Foster remained as acting first minister, after Peter Robinson stepped aside.

Under the current legislation, the resignation of the first minister would trigger an election in Northern Ireland earlier than the scheduled date, which is May 2016.

Secretary of State Theresa Villiers declined the DUP's request to pass an emergency law enabling her to suspend the executive, and the prime minister said there must be "intensive cross-party talks" to resolve Stormont's problems.

On 18 September, Ms Villiers announced that the government had commissioned a "factual assessment" from the UK's security agencies and the PSNI on the status of paramilitary organisations in Northern Ireland.

The DUP did not allow its Stormont departments to fall into the hands of any other Northern Ireland party.

Instead it kept them vacant by ordering its ministers to stage a series of resignations and reappointments on a week-by-week basis.

This "revolving minister" tactic incurred much public criticism, but kept the door open for the party's ministers to eventually return full time.