The Stormont stand-off over welfare reform has the potential to shut down the Assembly and Executive, First Minister Peter Robinson has warned.
His comments came after Sinn Fein leader Gerry Adams warned that with Westminster elections next May and the Assembly elections a year later, the political process is under its greatest challenge since the days of the Good Friday Agreement.
The politicial temperature was ratcheted up by the leaders of the two biggest parties ahead of the next Stormont spending round, which is expected to result in further departmental cuts.
Responding to a speech from Mr Adams, Mr Robinson said: "Once more we see the self-serving attempt by Sinn Fein to distract public attention from real problems by blaming everyone, except itself, for what it asserts is a crisis that impacts on the political institutions.
"This tired tactic does nothing to solve the problem most likely to bring down the political institutions."
The DUP leader went on: "People need to know that the Sinn Fein cuts will grow year on year and will amount to about £1 billion over the next five years."
Other unionists also accused Mr Adams of "bluster" and "cowardship" following his stark warning that the peace process was facing its most serious challenge in 16 years. And the Sinn Fein president's insistence that an inquiry into the Ardonye Orange march logjam would undermine the Parades Commission was also rejected by the DUP and Ulster Unionists.
Mr Adams argued that too many in the pro-Agreement camp – taking in civic leaders, the community sector, trade unions and business sector – had been too "passive", as had the Irish Government. "We are moving into another election cycle with the Westminster elections next May and Assembly elections the following year," he said.
"Elections invariably see unionist leaders adopt ever more strident language and an unwillingness to find solutions to difficulties.
"I believe that the political process faces its greatest challenge since the Good Friday Agreement negotiations in 1998."
The DUP's Gregory Campbell said Mr Adams had been exposed as a coward by refusing to reveal details of his own past.
And Ulster Unionist leader Mike Nesbitt said: "It is quite clear that Gerry Adams is blustering.
"This is clearly not the politics of the real world."
DUP Finance Minister Simon Hamilton has insisted the failure to implement the national welfare reform changes means this year's Stormont budget has already been reduced by £13m.
This will rise in the next few months to a total of £87m. The money will be taken out of the province's block grant from the Treasury – equal to the amount it calculates the reforms would have saved the public purse.