One in four Greater Manchester charities and voluntary groups which receive public money could close due to spending cuts, the BBC has been told.
Alex Whinnom, of Greater Manchester Centre for Voluntary Organisation, has warned 25% of 10,654 organisations, receiving funding, could be hit.
Most of the groups do not know if they will get money beyond March.
The voluntary sector employs an estimated 20,000 people in the Greater Manchester area.
These charities and voluntary groups receive funding from a variety of public sources including the police, primary care trusts or, more often, their local council.
According to Mr Whinnom, the drop in public funding due to the government's spending review will be drastic for such groups.
"I expect a quarter to disappear," he said.
Groups which have spoken to the BBC off the record said they were concerned that increasing unemployment would lead to an increase in people with mental health problems, more homeless people and more people with drink and drug problems at a time when councils are withdrawing support.
Liz Winsor-Welsh, chief executive of Voluntary Action Oldham, said the voluntary sector could not survive on goodwill alone.
"Even if you are thinking about services that are going to be run at a local level that aren't traditionally public services, those organisations still need funding of some sort.
"And as grants start to dry up and other public sector funding starts to dry up, it's really difficult, it's really difficult to see where that money will come from."