Is Titian's painting worth saving?

The campaign to prevent 'Diana and Actaeon' from being sold off assumes that it's a great painting. Tom Lubbock disagrees

So imagine if the Duke of Sutherland owned Milton's Paradise Lost. Imagine if the duke was offering it to us for £50m, and if we couldn't stump up he'd sell it to America, and then – if we wanted to read or hear or in anyway know Paradise Lost – we'd have to go to somewhere in America. Imagine, in other words, that a poem was like a painting, a unique object, which could be bought and sold like real estate.

What would be happening? We'd be hearing a great deal from Andrew Motion, saying how vital it was that Paradise Lost – one of the greatest English poems, what's more a piece of our heritage – should not leave the shores of its birth. Poets and professors would be signing round robins. What we wouldn't be hearing is that Paradise Lost was once and remains a controversial poem, whose value has often been questioned.

With poetry, disputes can be safely held. The poem is in print. Whatever happens, it won't be sold off and taken away. No individual or institution has anything material invested in the reputation of Milton. This is one reason why critical debates are more vigorous in literature than in art. There was a Milton controversy. When was there last a Michelangelo, Leonardo, or Titian controversy?

Titian's Diana and Actaeon needs no introduction. You know the campaign to buy it from the Duke of Sutherland for the National Gallery and the National Gallery of Scotland. You know the price that must be raised by the end of the year. You'll remember the round robin letter, signed by lots of artists, urging us all to chip in. You may also have been to see it during its temporary fund-raising showing in London, which came to an end last weekend. And now it looks very much like the needful £50m will be mustered from various public and private sources.

Well spent? I don't have a problem with the money. It's nothing to the sums that evaporate before our eyes everyday at the moment. It's certainly what the picture is "worth". £50m is a snip compared to what it would raise at auction. And if people want to buy it I don't want to stand in their way. My problem is how the campaign was conducted. You remember all the arguments advanced to persuade you that this was a very great painting, and vital to hold on to? No, me neither.

The case for Diana and Actaeon didn't begin to be made. It amounted to no more to the most general commendations. There was John Leighton, director of the National Galleries of Scotland, who called it "our Mona Lisa". There was Nicholas Penny, director of the National Gallery in London, who said it was "miraculous".

Lucian Freud declared: "I can't imagine anything more beautiful." A long list of artists – David Hockney, Bridget Riley, Frank Auerbach, Peter Blake, Paula Rego, Antony Gormley, Rachel Whiteread, Damien Hirst, Tracey Emin – agreed that it was "among the finest works in private hands in the world". And Colin Wiggins of the National Gallery said it was "one of the greatest works of art on the planet."

Convinced? This wasn't argument but blandishment, a series of glowing testimonials, which add up to: take my word for it, you jolly well better believe it. And if we couldn't raise the necessary, that would only prove what an art-blind nation of philistines we are. As the top Titianist Tracey Emin explained, delivering the letter to Downing Street, it would be "really embarrassing" if some foreigner bagged it.

Doubters were huffed into silence, or into a meek admission that, if they failed to appreciate the planetary greatness of Diana and Actaeon, that must be an fault in them. It's been a magnificent act of aesthetic blackmail.

Of course, when you're dealing with one of the greatest pictures on the planet, giving this or that particular reason why it's so good is likely to diminish it. The trouble with arguments is that they only allow counter-arguments. They give the unconvinced a foothold.

So, as one of the firmly unconvinced, let me make the first move. Let me say what I think is no good about this painting. Look at it. It's all over the place. It's cramped on the left where Actaeon comes in. It falls apart on the right among the goddess and nymphs. It doesn't have any strong focus or gesture.

The picture doesn't establish a decisive action. The central confrontation of Actaeon and Diana is hamstrung between his daft gesticulations and her flamenco flourish. It doesn't establish a defined space either. The setting is an inarticulate add-up of arch, trees, column, bodies. The sloping fountain, the ground area, make no clear sense.

It's cobbled together from bits and pieces in search of a structure. If ever a picture hadn't been worked out yet, it's this one. So, interesting perhaps as an example of a Titian in progress, but the opposite of miraculous. Or tell me I'm wrong. And tell me why.

There are spatial glitches that have no obvious point. Where exactly is the highly prominent pink hanging? It's held on to by a nymph who lies quite a way behind Actaeon. It's also almost in the right hand of Actaeon. Bodies are in confusion. Look at Actaeon's left leg, and the leg of the nymph behind him, and the chin of his black dog: the edges of these three items get muddled up.

Diana's extended leg (which is oddly shorter than her other leg) and the leg of the nymph who's drying it, get joined together, so that the nymph's lower leg looks like Diana's leg below the knee – and now this leg becomes bizarrely long. Is this effect good? Of course Titian, like any artist, can play these games. But to what benefit?

Perhaps none of these things matters. Perhaps the only thing that matters with Titian is flesh – his sumptuous, glowing, rolling oceans of flesh. He is the great painter of the body, the skin, the senses. Only a prude could resist the invitation.

But there is something wrong with these bodies. What substance are they made of? Something manipulable and something vague. It's a kind of putty and a kind of shimmer. It's neither resilient nor vulnerable. This is how Titian fantasises flesh, as a luminous pastry, and oil painting certainly lends itself to this fantasy. Diana and Actaeon is a textbook example of this unfortunate tendency in European art. It's one of the places it starts.

The planet, fortunately, has many greater paintings. Several are by Titian himself – for instance Bacchus and Ariadne and The Death of Actaeon, both already in the National Gallery. Diana and Actaeon is bad Titian. It would be no tragedy if we lost it. It has scholarly value. It's just the kind of thing that belongs in the Getty Museum in California. But what we've now bought for our £50m is not only the painting itself, but the perpetual obligation to believe it's a work of supreme genius. Bingo!