The SDLP leader has told a fringe meeting of the British Labour conference in Blackpool of his "deep alarm" at what he called the threats being made to the Belfast Agreement.
Referring to the decision by the Ulster Unionist Council to impose conditions on the party's participation in the North-South Ministerial Council and to threaten to withdraw from the Stormont Executive and policing structures if the IRA does not disarm and disband by January, Mr Mark Durkan said the tactics were a "demolition derby".
Speaking last night he said he shared unionist concerns about continued republican paramilitarism, but added: "I am deeply sceptical of the motives of unionist politicians vociferous about republican paramilitarism and yet silent on the even greater threat emanating from loyalism." He said the absence from the UUC's motion last week of any mention of loyalist violence was shameful.
Mr Durkan questioned "how threatening our constitutional structures will succeed in delivering the lasting peace we all want".
"Collapsing our institutions will punish the public, not the paramilitaries," he said. "They will be happy to be handed the whip hand over democracy."
The Deputy First Minister touched on the controversies most troubling to unionists, using the phrase "the scandal of Colombia" and the more guarded "questions of Castlereagh".
But he also suggested that at the root of current unionist tactics was a fear that the Belfast Agreement had initiated a one-way process of change from which unionists stood to gain little or nothing.
He insisted that the agreement delivered for everyone in Northern Ireland and was not about a zero-sum game between winners and losers.
"It is about undermining that false logic with a basic truth: when people work together, everybody benefits. That is a crucial message, one which unionist politicians should be - but are not - delivering."
He went on to describe the agreement as "a template for the Northern Ireland of today and a united Ireland of tomorrow".
"It is also why for unionism to forgo the agreement would be to risk forgoing not only their say in the Northern Ireland of today, but their position in a united Ireland of tomorrow."