Sinn Féin’s Martin McGuinness has said there should be no preconditions to any talks held between Northern parties to resolve the impasse that has brought the political institutions there to the verge of collapse.

He was speaking as he led a party delegation into meetings with Northern Secretary Therese Villiers and Minister for Foreign Affairs Charlie Flanagan: "I want to see, and am working for, talks to take place with a view to a successful outcome."

“If talks do not take place, or if talks do take place and there is no outcome, there should be an election,” he said.

The Deputy First Minister said that he was suspicious of an agenda in the murders of two men in Belfast this summer, both of them prominent republicans.

He referred to the possibility of “agents” against the Sinn Féin and republican project being involved but said he was not referring to state agents but something wider than that.

On Monday’s round of bilateral talks, Mr McGuinness said: “I think it’s very important that people recognise there are only really two choices. That’s either talks and a successful outcome or elections. That’s a stark choice that is facing the parties in this process.”

Both leading unionist parties, the Democratic Unionist Party and the Ulster Unionist Party, have indicated that they will not participate in talks unless certain preconditions are met.

The issue of Sinn Fein's continuing denial of the existence of the IRA will "kill or cure" the Northern Executive and Assembly, Ulster Unionist Party leader Mike Nesbitt said.

Mr Nesbitt also called for stronger measures by the British and Irish governments to tackle alleged paramilitary activity on both sides of the Border.

The UUP was the first of the North’s main parties to engage in talks at Stormont House today designed to resolve the crisis over the status of the IRA and also the deadlock over welfare reform.

The UUP leader again rejected the Sinn Fein assertion that the IRA is "gone away" notwithstanding the assessment by the PSNI chief constable George Hamilton that that some of its members were involved in the murder of Mr McGuigan although without the sanction of leadership.

“It was clear to us the Secretary of State agrees with our assessment that Sinn Fein’s continual denial of the existence of the The IRA is doing huge damage to the political process,” said Mr Nesbitt.

“If there is to be talks this I believe will kill or cure devolved government,” he added.

He indicated that while the focus today is on bilateral talks that the earliest round table talks could happen would be Wednesday.

“We have cautioned against holding round table discussions at this time until the Secretary of State gets a feel for where others, particularly Sinn Fein are,with regard the way forward,” said Mr Nesbitt.

The UUP leader said he had put proposals to Ms Villiers on how to combat crimes such as drug dealing and Border fuel laundering allegedly involving paramilitaries.

He suggested there could be a role for the British National Crime Agency - described as a UK version of the FBI - and for statutory agencies in the South in tacking such crime. He also indicated a reactivated or new version of the Independent Monitoring Commission could be employed to assess the status of the IRA and other paramilitaries.

Mr Nesbitt said one of the key issues was establishing trust. “There is no trust about Sinn Fein being themselves alone, about the existence of the IRA in 2015. The British government get that and they understand the damage that stance is doing,” he said.

SDLP Assembly member Alex Attwood, before entering the talks today, said the big test for the governments and the parties was to "get back to the fundamentals of the Good Friday agreement despite the damage done to them over the last 10-15 year".

Earlier Alliance leader David Ford confirmed his party would attend round table talks on Wednesday but criticised other artiest who have not committed

We must deal with the threat of violence as it exists on both sides of the community now and permanently.

Asked about other parties hinting they may not attend he said: “We no more need people playing silly games in and around Storming House than we need violence on our streets and the threat to all our community.”