Late last year, data-management company Occam asked five million donors to 24 charities, including the NSPCC, Amnesty International and Oxfam, about their giving habits.
It found that 80 per cent of committed givers - those who donate on a regular basis through direct debits, credit cards, standing orders or payroll giving - give to only one charity.
On average, those quizzed make 1.2 regular gifts. Occam claimed that if this figure were increased to 1.3 gifts per person, it would yield an extra £19m for the 24 charities surveyed.
Scott Logie, head of charities at Occam, said: "The results reveal that, although charities are increasingly good at recruiting committed givers, there is room for improvement in terms of extracting maximum value from these donors."
Telemarketing generates the largest number of donations by committed givers and door-to-door fundraising the fewest, the survey showed.
Occam found that people recruited by telemarketing gave 1.8 regular gifts on average. The next most frequent donors were those recruited through the internet (1.7 gifts) and direct mail (1.6 gifts). Those recruited by door-to-door methods gave on average 1.3 gifts.
The average annual value of gifts generated by both telemarketing and door-to-door fundraising stood at £68. Web donors gave £55 a year and direct marketing pulled in an average of £53. Payroll giving generated an average of £80 per person a year.
The survey also revealed that 60 per cent of committed givers were women, but that men each gave £10 more per year.