Charities were named as only the sixth most trusted British 'institution', with a 42 per cent trust rating.
This put them behind the armed forces (75 per cent), police (55 per cent), NHS (51 per cent), Scouts & Guides (50 per cent), and schools (46 per cent).
Confidence in charities tended to dip with an increase in age. Some 47 per cent of 16- to 24-year-olds trusted charities compared with just 35 per cent of 55- to 64-year-olds.
'These latest figures may well set nerves twitching throughout the sector,' said nfpSynergy's Joe Saxton. 'Only two in five British adults claim they trust our charities. Just nine months earlier, the majority said they did.'
He called on the sector to improve the reputation of charities. 'The sector cannot be ostrich-like and pretend the situation will improve on its own. We need to manage the reputation and image of charities and the sector proactively, backed by a clear communications strategy,' he said.
The Charity Awareness Monitor surveyed a representative sample of almost 1,200 people over the age of 16 throughout mainland Britain.