The umbrella body's report Calling for Change: the Evidence for Supporting Community Voices to Speak Out, due to be unveiled on Friday, will also say small groups are having to abandon community development work to provide services that generate income.
The study says relations between statutory and voluntary organisations must improve or there will be grave implications for the devolution and community cohesion agendas.
"It is very difficult for local and statutory organisations to enter into equal partnerships when the main authority to implement changes sits with the statutory organisation," it says.
A spokeswoman for the Office of the Third Sector said it was working to improve partnership between the sectors at local and national level.
"This research is a classic example of how government funding does not compromise the independence of the sector, but enables it to have a voice and campaign for change," she said.