Northern Ireland Secretary Shaun Woodward said the cross-community vote next Tuesday is nothing less than a vote for the future of Northern Ireland.
He was speaking at Edinburgh University tonight.
Mr Woodward said: ‘The responsibility on all MLAs next Tuesday cannot be overestimated. By voting to complete devolution they will be doing so much more than voting for the transfer of policing and justice powers from Westminster to Stormont, important as that is.
‘They will be voting for the hopes and aspirations of future generations who do not want to relive the past.
‘The last 12 years and more have shown that politicians and the communities they represent can overcome divisions that seemed to the world to be well nigh unbridgeable.
‘It would be unthinkable to falter at this stage. And it would be hard to forgive anyone who put all that has been so hard won at risk.
‘No one is suggesting that what has come out of The Good Friday Agreement, St Andrew’s and now the Hillsborough Castle Agreement is incapable of improvement’.
‘The architecture is there to enable locally accountable representatives to address the issues that rightly concern the people: education and skills, investment and jobs, policing and community safety. But the structures must be developed, not destroyed’, he said.
UUP not in position to back devolution deal
Earlier, the Ulster Unionist leader Reg Empey said his party would not be supporting the landmark deal to devolve policing powers to Northern Ireland in a crucial Assembly vote next Tuesday.
Speaking after a meeting of UUP Assembly members in Templepatrick, Co Antrim, he said the Hillsborough Agreement on law and order transfer and parading was not acceptable in its current form.
Although Sinn Féin and the DUP have the electoral strength to push through the accord when it is put before the Assembly on Tuesday, a ‘no’ vote from the UUP will deprive them of the unanimous support they seek.
The party's decision is potentially problematic for Britain's Conservative Party, which has an electoral pact with the UUP in Northern Ireland.
David Cameron is a supporter of the Hillsborough deal and he now faces the prospect of going to the polls aligned to a party which opposes it.
Mr Empey said the party's executive will meet on Monday night to hear a report from him and to take a final decision.
The East Belfast MLA said the Stormont Executive needed to demonstrate an ability to address other outstanding issues facing it - such as the uncertainty over education reforms - before it could be trusted with security powers.
‘It remains our view that the current Executive must be capable of exercising its existing powers before such an important issue as policing and justice is devolved,’ he said.
He and his colleagues have now sent a series of proposals to the other parties in the Assembly designed to tackle the matters of concern to his party.
He said he would examine any responses to that document over the next 72 hours and did not totally rule out a change of position ahead of Tuesday.
‘Over the coming days we will continue to monitor progress on matters contained within our document,’ he said.
‘The Ulster Unionist Party remains committed to devolution and to providing strong, stable and effective government for all the people of Northern Ireland’, he added.
Earlier the DUP leader and First Minister Peter Robinson said people in Northern Ireland wanted to see this issue put to bed and dealt with.
He said he believed they would react very badly to any party that tried to stop Northern Ireland moving forward.
Mr Robinson said the Hillsborough Castle Agreement represented a fair deal for Northern Ireland.
Devolution of Policing and Justice: an objective which every single party in the Assembly is committed to, can occur in a stable and safe environment, he said.
He said every single party in the Assembly was committed to the devolution of policing and justice powers and should therefore stand over their commitments made to the public.
He said he believed that the people of Northern Ireland were tired of political point-scoring and party positioning.
They deserve to see devolution working better, he said.
'Dismal failure of political leadership'
Deputy First Minister Martin McGuinness described the move by the Ulster Unionist Party as a dismal failure of political leadership.
Speaking at the Sinn Féin Ard Fheis, Martin McGuinness said some of the measures proposed by the UUP would see the return of unionist majority rule.
Mr McGuinness also said that playing politics with the future of the institutions is unacceptable.