The children’s charity Plan UK is in the process of contacting its supporters about potential data loss after the theft of five computer servers from its offices in London last week.
The servers contain information on supporters, including names, addresses, contact details, bank account numbers and sort codes.
The charity’s spokesman declined to reveal how many supporters were among these whose details were on the servers, citing police advice to disclose only limited information about the case.
The spokesman said a total of about 90,000 of its supporters sponsored children, which is its principal activity.
The charity said it had alerted the Charity Commission and the Information Commissioner’s Office to the theft.
Tanya Barron, chief executive of the charity, said it was informing supporters of the situation and providing advice.
"No credit or debit card details were obtained," she said. "Security measures on the data held means that obtaining the supporter information in these files would be very difficult."
Police are investigating the theft, in which entry was forced into a locked server room on the evening of Sunday 22 November.