One of the reasons I have enjoyed being president of the Museums Association (MA) is essentially symbolic. For most of the time I have worked in museums, there has been a rift between the big national museums and the regional, particularly local authority, museums, which have suffered a lot of cuts. Inevitably, they have looked with some envy at the ostensibly more privileged nationals. I hope that this tension has now been reduced.

Renaissance in the Regions has meant a new source of income and energy and a levelling of the divergence between the nationals and at least the big regional museums. Working together, one quickly realises that far more unites us than divides us; that we can learn from one another; and that we are participants in a common enterprise.

The biggest issue I have had to face as president is that of acquisition and disposal. During the past two years I have become increasingly anxious about the inability of the National Gallery to acquire great works of art. But this is a problem that afflicts us all because acquisition is, and always has been, central to our mandate.

We exist to conserve and preserve and hand on collections to the future. Of course, we are also required to display and interpret and educate and encourage new audiences to seek out and understand what we already own. But we have a responsibility to hand on the legacy of the past, as far as possible, intact.

I inserted the words 'as far as possible', because I cannot ignore the fact that there has been a change of mood towards de-accessioning. The Getty is currently selling 20 per cent of its original collection. The Kimbell Art Museum in Texas is a great collection because it made quite radical sales from its original bequest.

Over recent months, the MA has been faced by two extremely difficult issues regarding de-accessioning.

The first has been the proposal by the Watts Gallery to sell two works that are not part of its original bequest. In general, I am not sympathetic towards selling works when it is not directed at creating funds for new acquisitions. But the trustees of the Watts Gallery have looked carefully at the various alternatives and they have come to the conclusion that it is in their long-term interests to sell works that they do not regard as integral to the character of the institution. They have done this carefully and responsibly. Under these circumstances, I think that the ethics committee of the MA faces a very difficult balancing act in coming to its decision on the rights and wrongs of the trustees' action.

The second issue is Bury council's decision to sell a work by LS Lowry. This has not been motivated by a desire to enhance the collection or to stabilise the finances of the museum. It is simply to plug a deficit in council finances. This sort of decision is an act of arbitrary cultural vandalism because it breaks the public trust which is invested in museums. If Bury council does what it is still proposing to do without a vehement protest from the profession and, indeed excommunication from membership of the MA, then I fear that it will open the floodgates to all sorts of gratuitous and arbitrary sales, motivated by greed rather than responsibility.

I leave the presidency at a time when I think that museums are in good shape. But I cannot ignore the fact that there are black storm clouds ahead. I am full of admiration for what this government has done to fund educational programmes, to stabilise regional museums, and to ensure free admission to the national museums. But I don't want all these gains to be sacrificed on the altar of the Comprehensive Spending Review.

For me, the big issues are how museums face the changing trends of globalisation by developing a knowledge of local, national and ethnic cultures; how we capitalise on the digital revolution by providing access to deep information about the art and material culture of the past; and how we promote a deeper engagement with issues of identity, public memory and record, while remembering that we exist not just for the present but for the future as well.

Charles Saumarez Smith is the director of the National Gallery