Locking our Picasso away

This masterpiece is worth every penny of the £70m. But we are robbed unless it is kept on public display


A theft of world culture ... Pablo Picasso's 1932 Nude, Green Leaves, and Bust, sold at auction to a private collector. Photograph: Christie's/AP

The sale of Picasso's 1932 painting Nude, Green Leaves and Bust for a new world record price of £70m is a tragedy. Unless it turns out that the anonymous purchaser is a public museum – almost certainly not the case – what has happened here is a theft of world culture, art history and beauty from we, the people, by the super-rich. One of the last great surprises of 20th-century art has come and gone, photographed in the sale room on its journey from one private collection to another. If it appears in exhibitions in the future that will be the result of curators fawning to some billionaire for a peep at what, in reality, should be the cultural property of us all.

Public museums are miracles of redistribution. At London's Tate Modern anyone can walk in off the street and contemplate, for free, Picasso's great painting Three Dancers or Matisse's sublime cut-out The Snail. These works are as valuable, or more valuable, than the painting sold this week – but I can stand as close to them as any oligarch ever will. Andy Warhol said he loved hot dogs because even the Queen of England can't get a better one than the bum on the corner. At the National Gallery, the Queen of England can't get a better view of Leonardo da Vinci's Burlington Cartoon than me or you.

Yet it is becoming increasingly unlikely that museums will be able to add such artistic treasures to their collections, except through the occasional campaign to keep a painting in the country like the one that saved Titian's Diana and Actaeon from being sold abroad. If you look at the series of world records set by art sales over the past few years, they have something in common. From Klimt to Picasso to Giacometti and now back to Picasso again, the records are being shattered not by the likes of Damien Hirst but by the 20th-century greats.

The very qualities that make this particular painting so valuable are also the reasons its private acquisition for a price beyond any museum's purse is so depressing. It is a prime work by the supreme artist of the past three centuries (if you share my belief that Picasso was the greatest since Rembrandt).

While other pioneering modernists, such as Fernand Léger or André Derain, remain firmly in their time, Picasso is the kind of universal spirit whose art seems to transcend time – paradoxically, a timeless modernist. Just look at how the display in 2009 of a tapestry of his pacifist masterpiece Guernica at the Whitechapel Gallery captured imaginations. If, more than 70 years after it was created, this coruscating picture still strikes our century as an urgent depiction of war's terrors, then Picasso truly belongs among the Gods of art.

Nude, Green Leaves and Bust is a fine gift from this God – it would occupy a very honourable place among the treasures of MoMA in New York – however much we celebrate Tate Modern, still the world's best-stocked museum of modern art. It is a top-notch embodiment of Picasso's mind and passions at one of the cruxes of his career. In 1932 he was exploding into the shocking surrealist sensuality and orgiastic violence that would culminate in the creation of Guernica five years later: this is one of the key pictures of that moment of transformation and reinvention. In John Richardson's tremendous biography of Picasso there is a photograph of the artist standing in front of it: I wonder if Richardson should get a cut, for his words on this masterpiece must have been helpful to the auction house.

Museums such as MoMA and the Metropolitan in New York secured fine selections of Picasso's best works before the prices came near today's apocalyptic extreme. Now no museum in the world can seriously bid for a prime Picasso. This is particularly galling for Tate Modern – what a 10th birthday present it would be to add a painting like this to its collection.

Tate's glamour at least attracts private owners to make loans – who knows, perhaps we will one day see this marvellous picture in London through a collector's desire to be part of the Tate show. That is the best hope now of getting modern masterpieces for public collections – by charming the rich.

If you want to treat this as the market's verdict on art's true greats, Picasso deserves his top spot. But even as a fan I don't feel like cheering my hero. It would be better if he was neglected, better if the private collectors were going nuts for trite garbage. The bad news is that billionaires have taste. They are buying up the best of the 20th century, and leaving museums to make the best of papery displays of Fluxus periodicals and Futurist manifestos.