Peter Ireton, CEO of Bothar, says their charity has received hate mail and donations have halved in wake of top-ups controversy.
Speaking on RTE's Morning Ireland programme earlier today, Mr Ireton said the Central Remedial Clinic top-up scandal has "tarred" all charities with the same brush.
The Bothar founder said the charity's donations have halved since this time last year, which he blames on the salary top-up scandal.
He added that the charity has received hate mail in recent weeks, with most saying 'I'm not going to be paying your salary top-up'.
"I have never heard of a salary top-up until recent weeks," he said.
"[It's been] most distressing, especially for the young people in the office."
When asked whether the recession was a factor in this year's decrease in donations, Mr Ireton said he felt the top-up scandal was the sole fact, saying it came down "like a bomb" on them.
During the show, Mr Ireton said the charity does not receive any state funding for administrative costs. He added that they may have to consider putting salary costs online, but that it would have to be a board decision.
If people are concerned about where their charity donation is going, Mr Ireton suggested calling them to see.
"Please feel free to contact a charity. Most are just like us. They're very open and very frank," he said.
Last month, the CRC confirmed that money donated by the public was being used to top up salaries of well-paid staff.
The period in the run up to Christmas is typically the busiest time for fundraising in the year, according to Deirdre Garvey, CEO for charity representative The Wheel.
Ms Garvey told Independent.ie that this news from Bothar is this first connection being made by charity between a slump in donations and the top-up fallout.
"I would have said it's too soon to tell. We're hearing that fundraising is down, but we were hearing that before the CRC incident broke.
"That is the first one of our members that are making such a hardwired connection. It was already going to be an extraordinarily difficult winter. This has all the hallmarks of potentially being a disaster for charitable fundraisers," she said.