Why is it that so often when I visit a museum these days, I leave feeling ever so slightly cross? I’m thinking, say, of those wretched animatronic dinosaurs we parents have to queue for at the Natural History Museum, completely ignoring the genuine prehistoric skeletons either side. And of that display cabinet at the National Maritime Museum where nautical objects have been plonked apparently at random in the same glass case in order to illustrate a curator’s trendy post-modern point about the hopelessness of trying to extract meaning from artefacts so far removed from our own time and place.

But, hey, why pick on those two? Pretty much everyone in the museum world is at it these days and has been for some time: the exhibition at the Horniman, which proudly claimed - though with no supporting evidence, that voodoo was one of Africa's "great contributions to world culture"; the Gainsborough exhibition whose curator presumed to judge the mores of 18th century society by the PC standards of modern Britain; the decision by Manchester City Art Gallery to hang its paintings lower, the better that they might be enjoyed by children and the disabled; Palmer Majority Report (of which more later); the National Gallery's campaign to the keep Raphael's Madonna of the Pinks apparently less on the grounds of its artistic or historical merit than on its subject's status as a single mother; almost anything containing the words "access", "relevance" or "inclusivity."

What all these diverse irritants have in common is that they are part of the same worrying, hidden debate. "Hidden" because its arguments, though familiar to the point of cliche to anyone who works in the museum industry, are pretty much unknown to the people outside it. "Worrying" because the conclusions reached by these self-serving guardians of our national heritage are so often dangerously at odds with the needs of the public they claim to serve.

Someone in the audience of scholars, curators, directors and other museum professionals made this point rather well at an Institute of Ideas debate at the Wallace Collection last year on the subject Should We Junk Collections? "Most of us here are quite used to this sort of talk," she said, "But if it were to be overheard by the people who actually visit our museums a lot of them would be quite horrified."

She was referring in particular to the argument put by Maurice Davies - deputy director of the Museums Association - that museums ought no longer to consider it their primary duty to preserve their collections in perpetuity. Rather their main job should be to engage audiences with evangelical zeal, taking their collections out of the galleries and storerooms and into hospitals and schools, letting them be experienced and enjoyed by as many people as possible. And if one or two objects got damaged or even destroyed in the process, well, so be it.

To those of us reared on the fogeyish assumption that a museum's collection is sacrosanct - that the British Museum will always have its Elgin Marbles and the Pitt Rivers its shrunken tribal heads - the idea of ancient vases being mauled and chipped by mobs of primary schoolchildren or Roman coin hoards being flogged off to fund the acquisition of a more socially relevant collection of graffiti art is indeed a pretty shocking one. But for the new breed of museum professional, this line of thinking is very much the fashionable orthodoxy. Indeed, if you consult the Department of Culture, Media and Sport's strategy documents Museums For The Many and Understanding The Future, you'll find it's actually new Labour policy....