Sinn Fein chief negotiator Martin McGuinness has dismissed allegations that he is a British spy as a "load of rubbish".
The Mid-Ulster MP was speaking for the first time since former British army intelligence officer Martin Ingram made the allegations in a Sunday newspaper.
They come just months after former Sinn Fein official Denis Donaldson last year admitted he was a British spy. In April, he was found brutally murdered in Ireland.
After a meeting at the Stormont assembly today, Mr McGuinness was asked by reporters whether he was 100 per cent sure that the claims could not be backed up.
"I am a thousand, I am a million percent confident no one will ever produce anything against me. I have worked all of my adult life as an Irish republican," he insisted.
"Many of my comrades have been killed. Many IRA volunteers have been killed and I, of course, knew many of them, as many of you well know.
"Under no circumstances will I ever be concerned about anybody throwing anything up at me which will strike against me. It is not even a remote possibility."
Mr McGuinness was last week nominated by Sinn Fein to be the new deputy first minister of Northern Ireland, but the Democratic Unionist party (DUP) rejected the offer, which would have put DUP leader Ian Paisley in the post of first minister.
Today, Mr McGuinness suggested the DUP were behind the spy allegations, saying William McCrea MP had made a similar claim in the House of Commons in February, but it had been "widely ignored".
The DUP - who have refused to share power with Sinn Fein at the Stormont assembly, insisting the party has yet to give up its links with criminal groups - has rejected the suggestion.
However, Ian Paisley jnr said there should be some kind of investigation into the "amazing story" about Mr McGuinness.
Northern Ireland politicians are currently engaged in negotiations to restore some form of devolved government to the province, having taken their assembly seats earlier this month for the first time since Stormont was suspended in October 2002.
Sinn Fein are determined to press ahead with choosing a first minister and deputy and restoring full devolved power, but the DUP have refused to share power with the nationalists, and want the assembly to remain as a debating chamber.
Speaking to reporters today, Mr McGuinness suggested the allegations that he was a British spy were an attempt to distract efforts to restore power to Stormont.
"We are not going to be distracted. We are not going to be deflected and ultimately we are going to work through and I think our people have a very real sense that that is the case," he said.