More than a quarter of calls from voluntary sector workers to a whistleblowing charity last year concerned financial malpractice.
Public Concern at Work (PCaW), which provides support to people concerned about serious wrongdoing in the workplace, received 1,641 calls from workers last year, of which seven per cent (115 calls) came from the voluntary sector.
Of the calls from voluntary sector workers, the greatest proportion – 26 per cent (30 calls) – were about financial misdemeanours.
In comparison, 16 per cent of calls from private sector workers and 12 per cent of calls from the public sector workers concerned financial irregularities.
Ethical issues such as staff being drunk at work were the second highest reported problem by voluntary sector workers, attracting 21 per cent (24 calls) of calls, followed by callers who reported more than one problem, which attracted 17 per cent of calls (20 calls).
However, the charity said that the number of voluntary sector calls concerning financial malpractice had fallen in the past six months.
In the six months to May 2012, 19 per cent of calls were about financial malpractice, down from 32 per cent in the previous six months.
The charity said this did not necessarily indicate a real fall in financial malpractice, and might be because workers are less willing to speak out.
A PCaW spokeswoman said: "Given that government cutbacks have hit this sector hard, we are concerned that this drop is due to fear among voluntary sector workers inhibiting them from raising concerns regarding financial malpractice.
"Workers may be worried, particularly in the current economic climate, that by raising concerns they risk being ostracised in the workplace or even dismissal."
Nearly one-third of the 1,027 serious incidents reported to the Charity Commission last year involved fraud or money laundering.