Over £1 billion will be slashed from public spending in Northern Ireland between now and 2015, it has been claimed.
Any special case for the country to avoid the cuts could fall on deaf ears at Westminster, the Northern Ireland Council for Voluntary Action (NICVA) added.
Launching a major report on the challenges facing the economy, chief executive Seamus McAleavey warned frontline services could be at risk if the wrong approach was taken.
He said: "This is the most detailed external analysis yet of what is coming down the track and it makes for painful reading.
"It presents a significant test for our Executive and it is vital that the correct decisions are made.
"The choices made now will shape our economy and society for a generation."
NICVA is an umbrella organisation representing voluntary groups.
A report compiled for the NICVA by Oxford Economics, Cutting Carefully, said at least £1.2 billion would have to be saved between now and 2015.
The Northern Ireland Executive faces making £128 million in spending cuts following the emergency budget earlier this summer. It is not yet clear whether that will be incurred this year or next.
Earlier, £367 million of efficiency savings were announced for this financial year.