Charities' financial controls were found to be unsatisfactory in a third of all cases investigated by the Charity Commission last year.
Out of a total of 152 investigations undertaken by the Commission in 2001, 48 discovered problems with financial controls.
The figures emerge from a new edition of Charity Investigations, written by Andrew Burgess, partner at accountants Mazars, and published by Tolleys.
The most common reason for an investigation was a failure to submit accounts or file necessary returns with the Commission. In total, 38 per cent of all investigations concerned charities involved in education and religious work.
The largest number - 43 per cent - were instigated by the Commission.
Information from the public was responsible for another 32 per cent of investigations.
"Charities operate against a backdrop of financial constraints - too many needs and not enough money to meet them - and an increasing burden of regulation," said Burgess.