The Assembly will lose £123 million from its coffers as a result of Chancellor Alistair Darling's Budget today, with politicians divided over the true cost to the economy.

The Chancellor announced plans to make £9 billion worth of additional efficiency savings a year by 2013/14 while continuing to invest in public services.

But while Finance Minister Nigel Dodds confirmed the Executive will lose £123 million in the next financial year, he said it will receive £116 million in additional funding over the next two years.

Secretary of State Shaun Woodward added that when all the budget measures were taken into consideration Northern Ireland would make a net gain of around £50 million in the next two years.

But critics claimed that when further rounds of cuts were implemented the cost to Northern Ireland could rise as high as £450 million.

Mr Dodds said: "While, it is disappointing that Northern Ireland has not been allowed to retain the savings from additional efficiencies, I note that the net impact is less than had been feared as a result of the £50.3 million of additional funding for the Executive in the current financial year and £66.1 million in 2010-11."

He said the impact of the additional efficiency savings for Northern Ireland for 2011-12 and beyond will only become clear at the next UK Spending Review.

He added: "However, for the short-term we must continue to prioritise frontline services and focus attention on maximising savings from back-office functions and potentially inefficient institutional structures."

Meanwhile, Mr Woodward also revealed that government had agreed to give Chief Constable Sir Hugh Orde the millions he needs to help tackle dissident republicans with the first £28.7 million tranche of additional funding now available to the police.

But Assembly members were nevertheless concerned at the impact of the Chancellor's so-called efficiency savings.

Ulster Unionist deputy leader Danny Kennedy said the call for an additional £9 Billion of efficiency savings came on top of the £5 billion already in operation.

He said: "At this point the Finance Minister will have to get his head out of the sand and the Executive will have to urgently undertake a major revision of the priorities in the Programme for Government with job protection and job creation in mind."

Alliance Party Finance spokesman Stephen Farry said Northern Ireland faced a day of reckoning.

"This Budget provides a sobering measure of the depth of the current economic crisis and the austerity that will have to be incurred over years to come in putting things right today," he said.

"We will be entitled to a proportionate share from new financial commitments to training and employment measures and financial support for renewable technologies.

"Northern Ireland will therefore get a short-term financial boost from Barnett consequentials, in the range of £30m to £50m."

But he added: "In the longer-term, Northern Ireland risks taking its share of the announced £15billion 'efficiency savings'.

"Under the Barnett Formula, cuts of this scale would take £450 million out of our local budgets over the next few years."

A spokesman for the Secretary of State said the additional funds for police would ensure community policing was maintained.

He said the stark economic climate meant Northern Ireland would face additional financial pressures, as elsewhere in the UK.

He added: "But it is more than offset by the gains that have been negotiated."

Chairman of the Assembly's Finance Committee, Mitchel McLaughlin, warned the government against breaking pledges made to the Stormont administration.

"The Committee for Finance and Personnel is especially concerned at any potential move away from the negotiated settlement in the last Comprehensive Spending Review, as set out in the Executive's Budget for 2008 - 2011," he said.

"The Executive's Budget already provides for £800 million in cash releasing efficiency savings, which have been removed from departmental budgets for redistribution to frontline services and this presents departments with a significant challenge."

Speaking as a Sinn Fein representative, he added: "Sinn Fein believes that the only long term solution facing us on this island, both north and south, is a single strategy on taxation and regional and economic development.

"This budget as with previous British budgets will only serve to highlight the continued futility of partition and its detrimental impact on the lives of all citizens living here."

SDLP leader Mark Durkan said the budget was a mixed one for Northern Ireland. But he said the Executive had to respond to the new financial challenges it faced.

"The SDLP will be proposing the establishment of an Assembly committee to bring forward proposals to revise budget lines and spending profiles to ensure the best support for key economic sectors in the context of both the current downturn and future recovery," he said.

"Moreover we want to be able to explore innovative uses of public money to address the pressures caused by the global downturn and prospects for regional recovery.

"This committee should also consider proposals to ring-fence frontline public services and ensure more strategic targeting of efficiency saving."

Housing Minister Margaret Ritchie said the UK Government is investing an extra billion pounds in social housing and fuel poverty.

"I believe it is because he accepts the argument from people like me that social housing investment, in addition to tackling waiting lists and housing stress, is actually the best way to stimulate the economy," she said.

Secretary of State Shaun Woodward said the budget included an extra £27 million for Northern Ireland to boost measures such as winter fuel payments.

He said of the package: "In a time of serious economic difficulty this is a big success for Northern Ireland - for the Northern Ireland Executive, for the Police Service of Northern Ireland and most importantly for the people of Northern Ireland."