Haass was called on in September to help the main political parties end arguments over flags and parades which have caused rioting in the British province.
But Mike Nesbitt, leader of the pro-British Ulster Unionist Party (UUP) yesterday said, he had dismissed Haass's plans after a meeting of the party's 100-strong ruling executive.
Nesbitt called on First Minister Peter Robinson and his deputy Martin McGuinness - the unionist and republican at the head of the province's power-sharing government - to "clear up the obvious mess created by this process".
"We are committed to a better and fairer way forward, we don't believe Haass has cracked it, but it's up to Peter Robinson and Martin McGuinness to define a way forward for these talks," he added.
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McGuinness accused unionists of allowing extreme members to set their agenda.
The disputes are the legacy of the Troubles, the three decades of sectarian unrest between pro-British Protestants and Republican Catholics that largely ended in 1998.
The parties had set a December 31 deadline for an agreement.
However, he said there had been "significant progress" all round.
The seventh and last draft proposals by Haass were published on the Northern Ireland executive website.
The 40-page draft agreement showed that any form of a deal on flags was not even close.
Outbreaks of rioting over the past 12 months were the worst in Northern Ireland for years as community tensions over the marching season in the summer, when parades are held to mark historic dates, spilled over into violence.