Secretary of State Theresa Villiers has fired a warning shot over the long-running Stormont stalemate on welfare reform.
With the two main parties – DUP and Sinn Fein – still at loggerheads over implementation of the national changes, she insisted schools, hospitals and transport could lose out on future funding.
Earlier this week Finance Minister Simon Hamilton revealed Treasury penalties for failing to agree the shake-up, maintaining so-called 'parity' with the UK could amount to more than £1bn over the next five years.
Ms Villiers (right) said: "It's simply unsustainable to continue with a system that too often fails to reward those who work, parks people on benefits and has a cost which is spiralling out of control.
"But that's what Northern Ireland risks if it decides to break with parity and go it alone.
"It's reported that the Finance Minister now estimates that this could cost more than £1bn over the next five years ... money that could otherwise be spent on schools or hospitals or transport.
"Let me be clear. Our welfare reforms are designed to help people out of poverty by ensuring that work pays ... to tackle the causes of welfare dependency while being fair both to those in genuine need and the taxpayer.
"The Department of Work and Pensions has agreed a number of flexibilities with the Executive to suit circumstances here.
"I strongly believe this is the right reform for Northern Ireland and I hope the Welfare Reform Bill will start to make progress through the Assembly."
Speaking at a gathering of the British Irish Chamber of Commerce in Belfast, she said London is aware of the level of support in the province for corporation tax being reduced to the same headline rate as the Irish Republic.
"I agree that it has the potential to have a very significant impact ... but corporation tax, even if it is devolved, can't do it all," she said.
"Taken on its own corporation tax might not have anything like the desired effect unless it goes alongside other important measures to reform the economy and the way business is done here."
Prime Minister David Cameron will not take any final decision on devolving the powers to the Assembly until the autumn – after the Scottish independence referendum in September.
But First Minister Peter Robinson – who has said the measure could prove a "game-changer" for the economy – and Deputy First Minister Martin McGuinness have sought to maintain pressure on the Government since a verdict was delayed last year.
Ms Villiers also added: "Northern Ireland needs a planning system that operates in an effective and timely way. It's encouraging that the Executive here, under (Enterprise Minister) Arlene Foster, are now undertaking their own project to reduce red tape."
STORY SO FAR
DUP FINANCE MINISTER SIMON HAMILTON SAID IF NORTHERN IRELAND FAILS TO FALL INTO LINE WITH WESTMINSTER'S WELFARE REFORM IT WILL COST MORE THAN &POUND;1BN IN FUNDING OVER THE NEXT FIVE YEARS AND 1,410 CIVIL SERVICE JOBS IN BELFAST AND LONDONDERRY. BUT SINN FEIN'S ALEX MASKEY, CHAIR OF THE STORMONT COMMITTEE MONITORING THE SHAKE-UP, ACCUSED THE DUP OF "SCARE POLITICS". RECENT MEETINGS OF A MINISTERIAL SUB-COMMITTEE CHAIRED BY SOCIAL DEVELOPMENT MINISTER NELSON MCCAUSLAND HAVE FAILED TO MAKE PROGRESS.