Charitable donations have fallen by up to 40% since the revelations about salary top-ups at the Central Remedial Clinic.
Fundraising Ireland says the scandal is having a devastating impact on the entire charity sector.
The former CEO of the Central Remedial Clinic has resigned from the board - after it emerged he had been receiving significant top-ups from the charity - the Friends and Supporters of the CRC.
Colleen Dube, head of the Fulbright Commission here, a charity providing scholarships to students, said that it is important for charities to be upfront about how they conduct their business.
"I'd give to charities that I know are well run, and have transparency and integrity in how the remunerate their staff, use their admin budgets and direct the funding to the causes that are looked at," she said.
"So I would still continue to give to the charities that I know are doing things above and beyond question."