Guidance to help charities understand how to comply with the law and how not to irritate prospective supporters has been published by the Information Commissioner's Office.
The advice focuses on what organisations need to do to work within the Data Protection Act and the Privacy and Electronic Communications Regulations.
It follows research from the ICO showing that protecting personal information is now ranked as one of the three most socially important issues, behind only crime prevention and improving education standards.
Richard Thomas, the Information Commissioner, spoke about the findings in the annual Steele Raymond Lecture, held this year at Bournemouth University.
The guidance states that both the Act and the regulations affect the ways in which charities carry out unsolicited direct marketing.
It says: "Unwanted marketing is something many people find very annoying."
On the Data Protection Act, it advises that if a charity shares its marketing lists with other organisations, recipients need to be given information about who it will be shared with from the start.
The guidance also states that charities collecting information should give people an immediate opportunity to object to future contact.