Only one-quarter of charitable giving in the UK is tax-efficient, while donations as a proportion of income have fallen by 25 per cent in the past decade despite a rise in incomes.
The figures are revealed by the Charities Aid Foundation, which is hosting an event on 18 May to encourage wealthy individuals to donate effectively and more generously to charities.
Wealthy donors, according to Inland Revenue figures, give some £1bn of the £7.3bn given to UK charities each year.
"It is government policy to encourage greater giving, but the interesting statistic is that while the economy has grown by 25 per cent in 10 years, giving has fallen as a proportion by 25 per cent," said CAF's head of family philanthropy Graham Davies.
The foundation says that 'newly monied Russians' are among the new rich givers and are increasingly seeking to set up charitable foundations in the UK.