The Tate was among the best museums at collaborating

The Museums Association said that institutions were displaying a fifth of their collections at most.

The independent charity wants museums to put more of their artefacts on show, or to make them more widely available.

It said too many collections were "underused - not displayed, published, used for research or even understood by the institutions that care for them".

'Wider public'

The charity said it was not good enough for museums to keep spending public money on preserving objects that ordinary people were not able to enjoy.

In a report called Collections for the Future it suggested that museums should provide better access to people carrying out research.

Visitors are not being given proper access, it is claimed

They should also be more willing to lend objects to other venues, including schools and libraries, and to train staff able to "get the best from collections and share them with a wider public".

The Museums Association also criticised institutions for failing to collaborate properly.

It said that while some bodies such as the Tate and the Museum of London have good records on loans, many others have been reluctant to share both their collections and expertise.

The failings, the association warned, mean that "museum collections are one of our richest cultural resources but their full potential is not being realised".

In January then arts minister Estelle Morris warned that too many works of art and historical artefacts were hidden away.