Charitable donations from the top 100 philanthropists in the UK fell by almost a third to £1.67bn in 2009/10, according to this year's The Sunday Times Rich List.
Research conducted for the list, which will be published on Sunday, found that the amount donated by the top 100 by proportion of wealth given to charity had fallen from about £2.49bn in 2008/9 to about £1.67bn the following year, a fall of £818m.
However, the research, by the Charities Aid Foundation and The Sunday Times, also found that the number of donors giving more than £1m a year had grown from 118 to 129 over the period. The top 30 philanthropists gave away a bigger proportion of their wealth year on year, increasing from 3.22 per cent to 3.42 per cent.
Twenty-nine of the top 100 answered questions about their motivations for giving, and 89 per cent said they invested only in charities that could clearly demonstrate their impact.
Sixty-four per cent of those who responded to the questions said they were satisfied with the feedback they received from charities and 54 per cent said charities needed to improve their communications in order to meet their potential.
More than three-quarters said that personal experiences had influenced them to be charitable.
Jo Ensor, head of advisory at the Charities Aid Foundation, said: "There are many lessons here for charities that wish to interact with these philanthropists – notably, tailoring their communications and better demonstrating the impact of their work."
Top 10 philanthropists in the UK (wealth in 2011; what they gave 2009/10):
1. Anurag Dikshit (£35m; £172.4m)
2. Bart Becht (£90m; £80.2m)
3. Christopher Cooper-Hohn (£85m; £75.5m)
4. Richard Ross (£58m; £33m)
5. Dame Vivien Duffield (£40m; £19.4m)
6. Diana Ballinger (£58m; £25.6m)
7. Lord Fink (£120m; £33.1m)
8. Lord Sainsbury (£960m; £165.1m)
9. Sir Elton John (£195m; £26.8m)
10. David Potter (£40m; £4.9m)