The institute, which is currently holding a consultation on its direct-mail code of practice, is urging charities, donors and direct-mail agencies to submit their views on the subject by December.
Agencies have argued that incentives should not be included in a pack unless they are relevant to a charity’s mission, in order to prevent organisations from relying on ‘donor guilt’.
They also said charities should consider the impact of their direct-mail policies on the environment, such as the waste created by unwanted packs.