IN a sharp attack on the Tanaiste, the Ulster Unionist leader, Mr David Trimble, accused Mr Spring of "not living in the real world" by his "insistence" that the multi party talks could not move forward without Sinn Fein.
He also said if decommissioning was dealt with in committee it would "go into oblivion".
Mr Trimble, speaking to reporters at the Northern Ireland Forum in Belfast, also said it was unlikely his party would vote against the British government's partial ban on handguns in the wake of the Dunblane massacre in Scotland in March.
The issue of handguns for personal protection had to be considered and the Ulster Unionists "couldn't support a total ban", which the British Labour Party had called for.
On the talks, Mr Trimble accused Mr Spring of "frustrating everybody else" because his priority was finding a mechanism to include Sinn Fein. "That is not being sensible. I think it's about time Mr Spring got real."
The Ulster Unionists, he said, bad also made it "absolutely clear" that "there is no question of us going into committee" to deal with decommissioning "as a sort of fourth strand" of the talks which was being advanced by Mr Spring.
Once the issue was discussed in committee, under the rules of procedure the Irish Government and the SDLP would have a veto which would create a situation where nothing would be done, he said. "If decommissioning goes into committee, it goes into oblivion."
Mr Trimble said the British" and Irish governments were not agreed about the issue, adding that the British government's proposals were not clear. He was "not happy with the position made by the Secretary of State to the talks process this week". He said Sir Patrick Mayhew knew the proposals would not work.
"We want to get this matter resolved as quickly as possible, but progress is being held back because Mr Spring and the Irish Government will not make a commitment to talk to the parties in the process because his primary objective is to get Sinn Fein into the talks".
Asked about the ban on handguns, Mr Trimble said he wondered if the British Home Secretary, Mr Michael Howard, had turned his mind to the question of personal protection.
The response to the school tragedy and the Bill "is still largely an emotional reaction, understandably", he said, but "we have to look at things calmly". His party would like to see the government's proposals but he did not see it voting against them.
