Political relations between Sinn Fein and the DUP have become further strained after Deputy First Minister Martin McGuinness branded a U-turn on the redevelopment of a peace centre at the former Maze prison site a "mistake".
The major row between the two parties has now deepened after Mr McGuinness made scathing comments during a speech at a republican gathering at Balinamore, Co Leitrim.
It was the first time he had spoken publicly since First Minister Peter Robinson pulled support for the controversial project of the Maze/Long Kesh site last week.
Speaking on Saturday, Mr McGuinness said the decision to abandon the agreement reached on the future development was ignoring "political reality".
"It is a mistake not just because it jeopardises much needed investment and jobs, but also for the message it sends to the vast majority of people, nationalist and unionist, who are rock solid behind the peace process," he said.
"Some in the extremes of political unionism believe that they can unpick the Good Friday Agreement. Moves like this give them succour."
During the memorial parade for veteran republican John Joe McGirl, Mr McGuinness suggested the move was against the spirit of the Good Friday Agreement.
He added: "However, it ignores the political reality and ignores the fact that the vast majority of unionists want to see this process succeed."
The Maze/Long Kesh Development Corporation, the board overseeing the redevelopment of the former prison site, is now seeking "urgent" clarification about the future of the planned centre.
But DUP politicians say they does not regret the decision and stalling the project will not hinder the economic potential of the site.
MLA Nelson McCausland said: "The decision regarding the peace centre does not need to impact upon the massive economic potential of the site and the thousands of jobs which can flow as a result."
Fellow MLA Jeffrey Donaldson said there is still "great opportunity" at the site.
He warned Sinn Fein need to "accommodate views" if the upcoming Richard Haass talks – to address disputes including parades and flags – will succeed.
DUP MLA Edwin Poots also accused the Deputy First Minister of "absolute hypocrisy".
SDLP leader Alasdair McDonnell said the latest spat "sours the political process".
The DUP has faced public criticism from the Orange Order, the RUC widows association and other unionists over the centre.
The proposed peace centre at the Maze had been expected to open by mid-2015. Officials said it would create 5,000 permanent jobs on site in an investment totalling £300m.
Some unionist politicians and victims' families feared it could be turned into a "shrine" to IRA terrorism. Last week, the First Minister said it should not proceed without consensus.