Media playback is unsupported on your device Media caption Peter Robinson said he asked the prime minister to consider suspending the assembly

Northern Ireland's First Minister has urged David Cameron to suspend the Northern Ireland Assembly to try to resolve the current political crisis.

The request came after a motion by the Democratic Unionist Party (DUP) to adjourn the assembly was defeated.

The prime minister has asked for further "urgent" talks to find a way forward, Downing Street said.

The crisis was triggered by the murder of Kevin McGuigan Sr and a decision by the UUP to leave the executive.

The assembly is due to return next Monday after the summer recess.

But Mr Robinson said after an assessment by the Police Service of Northern Ireland (PSNI) of an IRA role in the murder of Mr McGuigan Sr it "cannot be business as usual".

The DUP's proposal for an assembly adjournment was brought before Stormont's business committee on Tuesday but was overruled by the other parties.

Mr Robinson led a DUP delegation to meet Mr Cameron at Downing Street on Tuesday afternoon.

'Rebuild trust'

Speaking after the meeting, the DUP leader said: "The government could suspend and we've asked the prime minister to consider that, if indeed the parties don't recognise an adjournment would be a better option."

In a written statement, Downing Street said: "The prime minister recognised the gravity of the current situation and the need to rebuild trust and confidence in the political process in Northern Ireland."

As such he has asked Secretary of State for Northern Ireland, Theresa Villiers, to hold further talks with the aim of agreeing a way forward, the statement added.

Analysis: What is the background to the Stormont row?

Stormont's power-sharing government returned in 2007, headed by then Democratic Unionist Party leader Ian Paisley as first minister and Sinn Féin's Martin McGuinness as deputy first minister.

The two men had been bitter enemies for many years, but the decommissioning of IRA weapons in 2005 and Sinn Féin's endorsement of policing in Northern Ireland paved the way for Stormont's return.

In the last assessment by the Independent Monitoring Commission, an official body that monitored paramilitary activity that was wound down in 2010, it said it believed the Provisional IRA had "maintained its political course" and "would continue to do so".

With Northern Ireland's chief constable now saying the Provisional IRA still exists and some of its members were involved in the murder of Kevin McGuigan, renewed focus has been placed on the stability of the institutions at Stormont.

Q&A: UUP withdrawal

Police believe IRA members were involved in the killing of Mr McGuigan, a former IRA man who was shot dead in east Belfast last month.

In the wake of the shooting, the head of Northern Ireland's police service said that the IRA still exists.

But the chief constable added that there was no evidence that the murder had been sanctioned at a senior level in the organisation.

That was rejected by Sinn Féin who said the IRA "had left the stage".

Northern Ireland's Deputy First Minister Martin McGuinness, who is also a senior member of Sinn Féin, said he took strong exception to anyone who questioned his commitment to peace.

He said his party had a strong record of condemning violence and said those who went armed with a gun were "no friend of Sinn Féin".

'Fast and loose'

He described the killers of Kevin McGuigan and Jock Davison as "criminals" and "violent dissidents".

Image caption Mr McGuinness said if the DUP followed suit and left the executive it would show a "massive failure of leadership" which would leave a "vacuum" of a "very real prospect of an increase in violence on our streets"

He also criticised the UUP's withdrawal from the executive and said the party were "playing fast and loose with the peace process".

Mr McGuinness said the UUP action was "all about the election" and said if the DUP followed suit and left the executive it would show a "massive failure of leadership" which would leave a "vacuum" of a "very real prospect of an increase in violence on our streets".

The DUP's proposal for an assembly adjournment was brought before Stormont's business committee on Tuesday.

But it was opposed by the UUP, Sinn Féin and the SDLP.

Media playback is unsupported on your device Media caption Theresa Villiers said it was crucial for the political parties to work together

The UUP's sole minister Danny Kennedy submitted his resignation from the executive on Tuesday.

'Real dialogue'

Meanwhile, Northern Ireland Secretary Theresa Villiers met the Irish foreign and justice ministers in Dublin to discuss the crisis.

She said it was important that political parties in Northern Ireland had "real dialogue" and worked together to resolve the future of the executive.

Image copyright RTE Image caption Charlie Flanagan said the parties in the executive needed to re-commit to the Good Friday Agreement

She added that it was "well worth considering" bringing back a body similar to the International Monitoring Commission to monitor paramilitary activity.

She also said it was important to bring paramilitarism to an end.

After the two-hour meeting, Irish Foreign Affairs Minister Charlie Flanagan said "no best interest was served" in allowing Northern Ireland's political institutions to collapse.

He said "a number of options" were on the table over how to rebuild trust among the parties, and added that there was a need for them to re-commit to "the spirit and the letter of the Good Friday Agreement".