Charities are likely to lose millions in income if the postal strikes continue into the Christmas period, according to a report by the Institute of Fundraising.
The report says that Epilepsy Action, which generated more than £3.3m last year, has already suffered a loss in income of £150,000 as a result of the strikes so far.
"A number of areas are affected by the mail strike," says the report, which is based on a detailed survey of eight members of the institute. "These include membership subscriptions, general donations, regular trust and corporate donations, fundraising events and the trading of Christmas cards and Christmas catalogues.
"For some charities the potential losses run into millions. If there is a backlog in the postal system, people will receive a large amount of mail when the strike is over and may be less likely to read and respond to appeals. People want to give before Christmas, not after."
Di Flatt, fundraising manager of Epilepsy Action, told Third Sector: "We are looking at other ways to raise money, such as Christmas e-cards. But we receive a higher proportion of donations by post in November and December than at any other time of year."
A spokeswoman for Save the Children said the charity might raise up to £1m less this Christmas than last because of direct mail not arriving, donors deciding not to send cheques and falling sales of charity Christmas cards.
Lucy Caldicott, director of fundraising at children's cancer charity Clic Sargent, said it could lose about £27,000 because of falling orders for Christmas cards alone. She said orders so far were 45 per cent lower than at this time last year. Danielle Atkinson, individual giving manager at medical relief charity Merlin, said the strikes that had taken place so far had affected the charity's income.
"With our September mailing, we normally receive 25 per cent of our target income by week four," she said. "It's now week eight and we have only 30 per cent of the target."
Talks are due to continue this week, but the Communication Workers Union is predicting more strikes for longer periods.