Some charities have seen donations drop by up to 20%, following negative publicity around Rehab and the CRC.
A survey of 297 charities has found that half of them have seen a fall in donations from the public since November last year, with a third having to cut back services.
The research was carried out by the Wheel, whose conference is currently underway in Dublin, with up to 300 charities attending.
John Dolan is the Chief Executive of the Disability Federation of Ireland, which oversees 120 charities.
He says his members have reported drops of up to 20% in donations, which severely affects what they do.