The National Museums Directors' Conference (NMDC) has identified engagement with issues of identity as an area in which museums can contribute.

The NMDC is also a partner in an Institute for Public Policy Research (IPPR) project aiming to "identify the policies that are most effective in challenging divisive identities and building shared identities, with a particular emphasis on the contribution that heritage and arts policy might play in fostering common identities".

Museums have two main roles in relation to identity: representing cultures from which their objects originate and acting as a form of identity expression in their own right.

There is a potential tension between these two roles, depending on the relationship between the museum culture and the culture of the objects - or the cultures of emerging identities, whether these are based on nationality, gender, ethnicity, race or sexuality.

Characteristically, the great museums of imperial nations, such as the British Museum or Russia's Hermitage, do not tell the story of their own nation. They represent their home culture as reflecting a universal aesthetic and rationality. They are not subject to definition; they do the defining.

Conflict arises in museums in terms of the differences between temporary and permanent displays. The former often engage with contemporary issues of identity, and are explicitly interpretive. The latter often reflect the museum culture of detachment.

Compare the National Gallery's exhibition in 2000, Seeing Salvation, with the galleries devoted to Islamic and Christian Art in the Victoria and Albert Museum or the African Galleries at the British Museum. In Seeing Salvation, instead of the traditional art-historical categories, the works were arranged to tell Jesus's life story. This did not deprive art-history fans of any pleasures, but it opened up the human and spiritual meaning of the objects.

The permanent galleries take opposite approach - detached and clinical. In terms of scholarship, they are up to date; in terms of identity, they could have been mounted at any time in the past 150 years. The issue at stake is one of power.

Museum culture also reflects social power structures. At the 2001 Museums Association conference, a senior manager from the National Gallery said the main barrier to making his museum more accessible was the friends' organisation. What's the point of joining a club offering exclusive access to precious experiences, if those experiences are given away to all and sundry?

Traditional museums validate group identities, but it is the identities of their visitors, not those of the cultures portrayed. Museum identity is also supported by the peer pressure on staff. Their group membership is dependent upon them representing their discipline from the inside, not using it as a resource of expertise which can illuminate human meanings in the objects for laypeople.

This is why the IPPR's view that "free entry to museums and galleries means that these are no longer the preserve of the metropolitan elite" is not only wrong - the three most-visited nationals never charged - but naive. Free entry helps, but the psychological and social barriers imposed by museum culture are far more significant.

The difficulty in changing museums at their heart - in their permanent displays - is one reason why emerging groups set up their own museums, with established ones missing the opportunity of becoming inclusive civic spaces.

Understanding the Future says museums need "to work with partners in academia and beyond to create an intellectual framework supporting museums' capacity to tackle issues of identity" and "continue to develop improved practical techniques for engaging communities of all sorts". To achieve this, museums will need to do five things.

Firstly, they must recognise the existing identity functions of museums and their exclusive and inclusive potentials. They must take on the challenge of bringing traditional constituencies into power-sharing arrangements with new groups.

They need to move beyond the usual museum disciplinary frameworks to human meanings. They must explore the difficulties of difference as well as emphasising what cultures have in common. And lastly, they must recognise that identities are inherently subjective.

Challenging "divisive" identities involves making value judgments about the cultures being portrayed. Credibility requires a self-critical approach in relation to museum cultures and their relation to inequalities.

While diplomacy and engagement with dictatorships are necessary, some focus on Tibet would be a counterbalance to the spate of exhibitions on China. Museums are well placed to explore the tensions between universal rights versus cultural diversity.

Mark O'Neill is the head of arts and museums at Culture and Sport Glasgow