When some bright spark at Tate Britain came up with the idea of doing a show about the history of Iconoclasm in this country why wasn’t the plan strangled at birth? Was there no one around to point out that the story of the dissolution of the monasteries has been told so often in books like Eamon Duffy’s The Stripping of the Altars that there isn’t a lot that’s new to say? Even if it proved possible to update the story to the present day, most of the visual material has long been destroyed or defaced. Did anyone at Tate think to mention that looking at photographs of works of art that no longer exist rarely makes for a satisfactory gallery-going experience? And finally, did it occur to the director to take the curator responsible for the section on modern art aside and explain to her what the word “iconoclasm” is usually taken to mean?

Obviously, the answers to all these questions is “no”. If you decide to visit Art under Attack don’t expect to see much in the way ofart, don’t expect to learn anything new, and don’t expect to enjoy the experience.

The exhibition starts with the familiar story of the dissolution of the monasteries under Henry VIII, then moves on to sacrilegious annihilation of religious imagery by the government of Edward VI. So effective was the order to “utterly extinct and destroy” religious images, that the first gallery is relatively empty, apart from a sad miscellany of mutilated fragments of sculpture, shards of stained glass, and savagely defaced paintings – each and every one a sickening reminder of how much of this country’s visual culture was lost during the Reformation. The deliberate destruction of any work of art is distressing, but since the reformers focused on sacred images, the sense of violation is even more acute. In front of a decapitated Madonna or the viciously scratched face of Christ, your instinct is to avert your eyes as you’d do in front of a mutilated corpse.

As it happens a mutilated corpse (or the representation of one) is the most eloquent work of art in the entire show, a limestone figure of the Dead Christ carved by a Netherlandish sculptor working in this country in the first quarter of the 16th century. No reproduction can begin to suggest the overwhelming power of the realistically carved torso and head of Christ’s body in transitu (that is, during the period between His death on the Cross and the Resurrection when the flesh was subject to corruption like any other corpse). We look down not on a divine personage but on a human cadaver in the early stages of rigor mortis.

After the reformers had hacked off the figure’s right arm, legs, and feet they stopped their foul work. I’d like to believe that it is a tribute to the artist’s skill that they could not bring themselves to smash a face that with its half -closed eyes and open mouth is so expressive of vulnerability, suffering and resignation.

Almost as eloquent is a mid 17th century painting showing the stripped down interior of Canterbury Cathedral. At first you think that the worst is over because all the images have already been obliterated by Puritan zealots.

Then with a sinking feeling in the pit of your stomach you spot the tiny figures high up in the clerestory of the nave, systematically smashing the remaining stained glass windows with pikes.

The exhibition then looks at a far less disturbing form of iconoclasm – the destruction of images for political reasons. Did any of us care when Saddam Hussein’s statue was overturned by a mob in 2003? Of course not – because the Iraqis weren’t destroying a work of art but a political symbol. We may regret the destruction by Irish nationalists of Grinling Gibbons’s Equestrian statue of King William III in 1926 or the loss of Nelson’s monument in Dublin’s O’Connell Street in 1966, but we can at least understand why they were targeted.

When Mary Richardson took a meat cleaver to Velasquez’s Rokeby Venus in the National Gallery she did her foul work on a “free day”, as if to emphasise that her purpose was to take the picture away from the British people of whatever age, sex, or class until the demands of the suffragettes were met.

Richardson, like all women who participated in iconoclastic campaign of 1913-14 could have attacked a statue or portrait of an MP opposed to votes for women. Instead they mutilated pictures in public museums, often chosen at random.

Richardson’s fatuous words of self -justification “you can get another picture but you can’t get another life” reveals just how little she knew or cared about what she was trying to destroy. Her sole purpose was to draw attention to her cause. That her cause was a noble one is irrelevant.

This is why I read the catalogue essay on the suffragette campaign with incredulity. The author, whose degree is clearly not in art history but in gender studies, describes these iconoclastic acts, “not as vandalism against the nation but as vital contributions to the freedoms now perceived as inherent to British national identity”. She concludes by denying that these iconoclastic acts were about destruction but instead “a creative process”.

This pernicious drivel amounts to an open invitation to any person or any group with a grievance to target works of art hanging in national museums.

The next time the guards at Tate Britain encounter an axe- wielding animal rights activist, a paint-hurling environmental campaigner, the divorced father with a hammer in his hand, or the radical vegan with a little knife, it will serve the gallery right if they decline to intervene in what a publication by the gallery they work for describes as a “creative process”.

Modern iconoclasts are motivated by a thirst for publicity that’s easily gratified by running amok in an art gallery. It all started in 1976 when a pompous ninny called Peter Stowell-Phillips splashed blue food dye on Carl Andre’s Equivalent VIII on the grounds that as a tax payer he objected to its purchase by Tate. Since then we’ve seen attacks on the works of Damien Hirst, Mark Rothko, Anish Kapoor and Tracey Emin, most of which were carried out by failed artists. However they try to justify what they’ve done, their actions are always selfish, always self-serving and never forgivable.

The subject of aesthetic vandalism is therefore an enormously interesting one, which is why the section of the show I most looked forward to was the last. Unfortunately this final section isn’t about what is normally meant by iconoclasm. It looks instead at artists who have made art by destroying something as opposed to constructing it. Examples include Robert Rauschenberg’s erased drawing by Wilhelm de Kooning and the moment when Michael Landy pulped an art work by Chris Ofili along with the rest of his possessions. Plenty of artists including John Stezaker and Dinos and Jake Chapman alter inferior art works to create greater ones. But this isn’t iconoclasm. And what on earth does Raphael Montanez Ortiz’s work have to do with iconoclasm? The objects he destroyed were not works of art but chairs and pianos.

Long before this I began to lose faith in this exhibition, which is poorly conceived and badly thought through. It certainly raises a lot of questions, but then so would a book or symposium. I guess I just like to look at things.

From October 2 to January 5 at Tate Britain, Millbank, London, SW1P 4RG. Tel 020 7887 8888