A story about Sinn Féin's Martin McGuinness, which appeared in last weekend's Sunday World, has been a discussion point for much of the week, while being greeted with widespread scepticism. The newspaper quoted a man who uses the name Martin Ingram and claims to be a former British army intelligence officer. He alleged that Sinn Féin's chief negotiator had been a British spy known as "Agent J118" in the 1990s. It was Ingram who first claimed that Freddie Scappaticci was the British spy known as "Stakeknife" and, while this claim is now widely accepted, few if any were prepared to countenance the suggestion that Mr McGuinness is anything other than an out-and-out republican.

Sinn Féin strongly refuted the allegations against Mr McGuinness, the MP for Mid Ulster. A spokesman said, "We have heard this all before. It is rubbish. It is all nonsense. Anybody with half a wit will treat it with the contempt is rightly deserves". It was Tuesday before Mr McGuinness bothered to comment and then he was quite dismissive, using the words "absolute hooey". He was "a million percent" certain that no evidence could be produced to back the allegation. The feeling in Sinn Féin appears to be that it is a DUP generated story aimed at making the re-establishment of a power-sharing executive more difficult. Gerry Adams also suggested the involvement of "old guard elements" within the security forces, trying to stall progress and perhaps hoping to have Mr McGuinness assassinated.

Mr McGuinness has blamed sections of the Rev Ian Paisley's Democratic Unionists who, he said, want to wreck the Northern Irish peace process.

He said: "I don't have any illusions whatsoever that the people behind this are hoping that I will be killed."

Mr McGuinness, the IRA's second in command in Londonderry when British troops shot dead 13 civil rights marchers on Bloody Sunday in 1972, was outraged by the allegations made by an operative who uses the pseudonym Martin Ingram.

"I was absolutely disgusted. I was very angry and I am still very angry. But the important thing is it hasn't worked," he told Irish State radio RTE. "The amount of support I have received from all over Ireland is absolutely incredible. My family has been hurt and they like me are angry about it, but there isn't anything we can do about it.

"I'm not accusing all of the DUP of being involved in this. I am accusing a certain element within the DUP who are doing their damnedest to prevent an agreement.There are people within the DUP who can't bring themselves to recognise that the future will be Ian Paisley and Martin McGuinness in the Office of First and Deputy First Minister."