The Individual Giving Survey for 2006/07 found significantly fewer men donating than in the previous year.
In 2005/06 the proportion of men giving to charity was 53 per cent, but in 2006/07 it had fallen to 48 per cent. This was a greater decrease than the general reported dip in the proportion of the UK population giving to charity, which fell by three percentage points over the same period (Third Sector Online, 10 December).
The amount donated also fell by three percentage points.
Dr Patricia Walls, research officer at the umbrella body the NCVO, said: "This trend has been found consistently over time and with some other countries.
"It's very difficult to know why there have been significantly fewer men giving last year, and why men have different giving habits in the first place."
She said it might be because women report household as well as individual giving.
The report also said that more than two-thirds of direct debit donations are Gift-Aided, compared with less than one-third of cash donations. People giving to overseas causes are more likely to give to religious ones, and vice versa, the report said.