Northern Ireland has been pledged up to £53 billion (€79.3 billion) over 10 years to underpin the St Andrews Agreement.
Chancellor of the exchequer Gordon Brown and Northern Secretary Peter Hain announced the investment strategy following a meeting with the Northern parties at 11 Downing Street last night.
Mr Brown insisted the expenditure, equivalent to about £50,000 (€75,500) per household, was conditional on adherence to the British and Irish governments' timetable for restoration of powersharing at Stormont.
The main parties will today be examining the detail of the proposals, but last night there were early concerns about the level of "new money" being offered over and above existing government commitments.
There was also widespread concern over the absence of any reference by the chancellor to reducing the Northern Ireland level of corporation tax from 30 per cent to nearer the 12.5 per cent which applies in the Republic.
The DUP told The Irish Times late last night the investment offered was "billions short" of what was needed. Ian Paisley jnr, echoing earlier remarks by deputy leader Peter Robinson, said the issue of a sufficient package could break the governments' efforts to restore the Stormont institutions by their target date of March 26th.
The Taoiseach welcomed Mr Brown's announcement as "another significant positive step forward" in the process towards a lasting settlement in Northern Ireland.
"It is an essential part of the St Andrews Agreement. It clearly shows what can be achieved when the Northern Ireland parties work together. It is important that the parties continue their collective engagement with the Treasury with a view to following up on today's announcement."
Mr Brown indicated £35 billion (€52.37 billion) would be made available over four years, beginning next April - shortly after the March 26th deadline for an Executive involving the DUP and Sinn Féin "going live" at Stormont. The remaining £18 billion would be allocated during the 10-year period from 2007 to 2017.
With departmental expenditure in Northern Ireland currently running at about £8 billion a year, some politicians contacted last night by The Irish Times believed that perhaps just £3 billion of "new money" would therefore be available between 2007-2011.
Mr Brown made clear the importance of restoration of devolution and the need to adhere to the British government's radical programme of public sector reform in Northern Ireland.
The investment, he added, was needed "to do more on social and public services and the reform of them and to build the infrastructure necessary for the economic development of Northern Ireland".
The chancellor said the package was "subject to agreement [ to the St Andrews Agreement by the Northern parties] on November 10th".
The parties expect to receive written details of the Brown proposals later today and are hoping to ascertain how much extra investment is being planned.
There was general dismay among the parties at the apparent refusal to reduce corporation tax levels.
British sources made clear they are resisting a precedent of cutting taxes for one region of the UK in order to help establish a local competitive edge.
The DUP was particularly critical of the proposals, insisting the unionist electorate's support for the St Andrews Agreement "could not be bought" and neither would they be satisfied with what was on offer.
Sinn Féin president Gerry Adams described the offer as "a peace dividend of sorts".