Fresh tensions today surrounded plans to devolve policing and justice powers from Westminster to the Northern Ireland Assembly.
Sinn Fein and the Democratic Unionist Party (DUP) had agreed a deal on the move, with speculation that the process could be completed in the autumn.
But as the parties edged towards a final resolution of the long-running dispute that once threatened to derail the fledgling government, the Ulster Unionist Party (UUP) today said the transfer of powers should be delayed for five years.
The UUP issued a report today claiming the Stormont finances were already under great strain and said the Assembly may not be able to take on the additional financial responsibility.
Ulster Unionist David McNarry said: "Any financial package for the transfer of policing and justice powers needs to be rigorously tested for its financial sustainability, risk management and contingency planning against potential shortfalls and it should be rolled out over a five- year period, initially being funded entirely by Westminster.
"Only then, on the basis of the outcomes of this five-year period, should it be fully transferred."
Prime Minister Gordon Brown recently ordered officials from London and Belfast to complete a financial package to help create a new Ministry of Justice at Stormont.
The Northern Ireland Executive recently passed draft legislation as a further step towards completing devolution.
Divisions between the DUP and Sinn Fein on the issue blocked Executive meetings for five months last year until a compromise deal was negotiated last November.
While the deal did not set a deadline for the transfer of powers, there has been speculation it would be completed this autumn.
The UUP proposal to instead phase in the transfer of policing and justice powers over five years came after DUP leader Peter Robinson said he would require cross-party support at the Assembly before completing the devolution process.
Sinn Fein Policing Board member Alex Maskey said the transfer of powers from London was part of the St Andrews agreement that paved the way for the creation of the power-sharing government.
"It is not an optional extra. It is a British Government obligation," he said.
Sinn Fein has called for swift action on devolution of the powers and today dismissed the UUP call.
"As it stands, an agreement on the process to deliver policing and justice powers is in place," Mr Maskey said.
"Those of us committed to making this process work and these institutions deliver for the people will simply get on with the real work."
The nationalist SDLP's Alex Attwood criticised the UUP proposal.
"Peter Robinson...was sharing his veto over the timing of that devolution with the UUP. Today the UUP has given its response," he said.
"The UUP says there should be a five-year testing period before the full devolution of justice.
"The UUP will find it hard to pull back from this and Peter Robinson's view appears to be that he won't jump without the UUP."
He called on the unionist parties to support devolution of policing powers so politicians could shape the justice system to meet public concerns on crime.
Ulster Unionist Policing Board member Basil McCrea said: "Alex's (Attwood) response to the UUP's proposal is disappointing.
"Policing and justice have been matters of great controversy and division in our society.
"To mishandle the devolution of those powers would threaten both political stability and the proper functioning of law and order."
The Alliance Party is tipped as the neutral candidate likely to be asked to take on the new Justice Ministry, with Sinn Fein and the DUP both agreeing to step aside.
"This paper shows up the lack of leadership on the part of the UUP. Rather than a 'can do' party, the UUP are now intent on becoming the 'can't do' party," said the Alliance party's Stephen Farry.
"Northern Ireland is now ready for the devolution of policing and justice. Rather than bringing more instability to the institutions, devolution itself will bring responsibility."