Charities that operate membership schemes should update them to ensure they are relevant to modern society, according to research by the National Council of Voluntary Organisations and the Royal Society for the Encouragement of Arts, Manufactures and Commerce.
The organisations carried out a year-long study involving 12 charities that run membership schemes, including the National Trust, the RNLI and the Scout Association, looking at the future of membership in the voluntary sector.
The study concludes that public perception of membership remains positive, but the structures of the membership schemes are in some cases outdated.
Social networking websites present opportunities for membership organisations because they can help them reach new audiences. but are also a threat because they compete for people's attention, the report says.
It adds that charities should stress the collective benefits of membership and the sense of belonging and identity it provides.
Stuart Etherington, chief executive of the NCVO, said: "We believe that getting people actively involved in causes they care about is the basis for strong communities.
"This means our members are our sector's greatest asset and it is important we continually review the way we work with them to ensure we provide attractive benefits and communicate through the most appropriate channels to maximise their potential."