The United Unionists insist a majority of unionists will today vote against the Belfast Agreement and the British government will then be forced to talk to the No campaigners.
They claimed private Northern Ireland Office opinion polls support their assertion that most unionists would vote No.
They said they could not have fought a better campaign despite "mind manipulation" from the British government and the media.
Eight of the nine unionist MPs in the No camp yesterday signed "the Declaration and Pledge of the United Unionists" at Orange Order headquarters in Belfast. The Order's Grand Master, Mr Robert Saulters, read out the declaration, saying that after careful consideration, his organisation had decided the document would not bring peace.
"We solemnly pledge and urge our fellow citizens to ensure, by every lawful means, the rejection of an agreement designed to destroy the Union," the declaration reads. The only anti-agreement MP absent was Mr Jeffrey Donaldson of the UUP.
At a United Unionist press conference earlier, the Rev Ian Paisley predicted the anti-agreement MPs whom the British government had "ignored" during the referendum campaign would be in demand after the votes were counted.
"After Saturday, Mr Blair will be very glad to see the leaders of the No campaign. He will be asking to see us before we ask to see him," he said.
The DUP deputy leader, Mr Peter Robinson, described Mr Blair's promises to the people of Northern Ireland as "not worth tuppence".
He said: "Mr Blair is a diminishing asset in the Yes campaign.
The dissident Ulster Unionist MP, Mr Willie Thompson, said assurances from the British government were worthless. Unionists has been promised Sinn Fein would not be allowed into talks without decommissioning.
They were then told there would be decommissioning during the Stormont negotiations and there wasn't. "We didn't believe them then and we don't believe them now," he said.
The chairman of the British Conservative backbench Northern Ireland Committee, Mr Andrew Hunter, attended the United Unionist press conference to voice his opposition to the Belfast Agreement. "I regard it as a triumph of terror. I see it as an assault on the essential Britishness of Northern Ireland," he said.