A study of five large organisations showed a correlation between gifts and the number of different interactions between charity and supporter, such as campaigning, volunteering, and correspondence.
The research, carried out by Adrian Sargeant, professor of non-profit marketing at Bristol Business School, found that active supporters give more and are more likely to recommend the organisation to friends. They are also less likely to give to other causes.
Paul Farthing, managing director of agency Target Direct, said Oxfam had increased its number of activists five-fold after asking donors to become campaigners.
The study also revealed there is no relationship between how much somebody gives to an organisation and how much they earn. An analysis of the five organisations' databases showed no link between the amount given and donors' incomes.
Also, so-called committed givers - those who pay a regular amount by direct debit - are in fact no more committed in terms of how much they give to a charity than those who give cash.
Sargeant described the findings as "very sad". "We are asking people irrespective of their income for the same amount of money," he said. He urged organisations to be upfront about asking higher-income givers for a larger amount appropriate to their income.
Delegates heard that the new self-regulatory framework for fundraising, based on the Buse Commission report, had been approved by a committee including all the main sector bodies.