Charities whose supporters receive a lot of mail from other charities attribute this cross-over to their supporters choosing to be generous to multiple causes or featuring on cold lists of likely donors – not the swapping of donor data by charities.

Royal Mail figures released to CivilSociety.co.uk last week showed that over the Christmas-New Year mailing period, September 2010 to February 2011, millions of pieces of mail were sent to supporters of major charities like Cancer Research UK, NSPCC and National Trust by other charities. A Royal Mail spokesman said that this was the result of charities mailing those donors who they feel are most likely to respond, rather than poaching others’ supporters. The charities with high levels of cross-over have agreed.

NSPCC and National Trust are among the large charities who say they do not share supporter data with other charities. Even so, Mike Flynn, head of individual giving at NSPCC, said that the majority of NSPCC supporters give to other charities and a significant proportion do so regularly. Flynn said that the charity, like others, had seen acquisition results decline in channels such as direct mail and DRTV.

Maria Gara, senior direct marketing manager at the National Trust, said: “In very simple terms, we do not share data - a practice which was more prevalent some years ago within the charity sector and not seen now as best practice. There is likely to be some natural cross-over in the Trust's supporters and other charities, and research shows that many of our members belong to more than one membership organisation or charity. As such it's inevitable that they will receive many mailings and it is perhaps surprising that our 3.8 million members will have had as few as eight million-plus pieces from other charities.

“It is also likely that these are people who would fall into a particular profile of donor who feature on a cold list bought by companies/charities with the same need for targeted, responsive audiences as us. That is not something that we can control.”

Cancer Research UK and British Heart Foundation both said that given their organisations' broad appeal and supporter base, it is only natural that their supporters will show up on other charities’ mailing lists.

Nick Georgiadis, head of direct giving at Cancer Research UK said: “As the UK’s only charity dedicated to beating all types of cancer, we have many supporters.  These generous people also support other worthwhile causes.  It’s no surprise, then, that they receive appeals from a variety of charities at Christmas - a key fundraising period for many organisations.”

Kate Shanley, project director for acquisition fundraising at the British Heart Foundation, said: “We are a large charity with millions of supporters, and direct mail has consistently proved a popular form of fundraising for us. Many of our supporters are touched by heart disease but it is highly likely that there are also other causes which are important to them so it’s not surprising that many receive mail from other charities too.”