Northern Ireland's chief justice will give his assessment today on transferring policing and justice powers to Stormont.
Lord Chief Justice Sir Brian Kerr is to give evidence to a committee of MLAs examining the proposed devolution of responsibilities from Westminster to the powersharing administration in Belfast.
But Jeffrey Donaldson, the Democratic Unionist chairman of the Assembly and Executive review committee, insisted that the May 2008 timetable was too soon.
Mr Donaldson, who stressed he was speaking as a DUP spokesman, claimed that public confidence in such a major move had yet to be established.
Citing an opinion poll that found only 14 per cent of the public backed the plan, he said: "As things stand at the moment, [ it will not happen]."
With his party leader and First Minister Ian Paisley holding a power of veto, the Lagan Valley MLA insisted nothing can happen without DUP support.
"We have secured a triple lock.
"The First Minister has to approve devolution; then it has to get approved by the Assembly on a cross-community vote; and then by parliament," Mr Donaldson said.
The transfer of policing and justice powers is one of the most contentious issues still to be resolved by the Stormont powersharing Executive.
Even though the DUP and Sinn Féin have confounded expectations by successfully governing the North together, many unionists still have deep reservations at the prospect of a republican being in charge of such a department.
As part of its work the Assembly and Executive review committee has to report on preparations for devolving responsibilities by next February.
It will also hear evidence tomorrow from Sir Desmond Rea, chairman of the Northern Ireland Policing Board.
Then, on Wednesday, Northern Ireland Secretary Shaun Woodward, who will eventually make the decision on devolving policing and justice powers, is to go before the committee.