The two "untouchables" of Britain's national museums and galleries, Neil MacGregor and Sir Nicholas Serota, have been criticised in a public attack by one of their peers.
Mr MacGregor, the head of the National Gallery and soon to be head of the British Museum, is virtually never criticised in art circles.
But yesterday Julian Spalding, the former director of Glasgow Museums and Manchester City Art Gallery, accused him of "stifling" the National Gallery.
Sir Nicholas, the director of the Tate, is a more controversial figure, but his detractors have usually been art critics rather than his peers. However, he too is attacked by Mr Spalding.
In a new book, The Poetic Museum: Reviving Historic Collection, Mr Spalding accuses Mr MacGregor and Sir Nicholas of doing a deal that has prevented the public from seeing coherent and cogent collections. Mr Spalding said yesterday: "Neil has agreed to let Tate Modern become the national gallery of post-19th- century art. A key change of policy has been made without any public consultation. This ought to have been discussed publicly. It has changed the nature of the National Gallery to have a cut-off date. I think he let Serota talk him into it.
"Neil has stifled the institution he so effectively nurtured. It is also bad news for the great painters of Britain. The likes of Freud and Hockney could expect after their deaths to have their paintings hanging in the National Gallery. They wanted to be measured with the greats. Now this can't happen and not many people realise it."
Mr Spalding believes there is a deeper malaise. "The National Gallery is beginning to die," he said. "And the tragedy is that it is being killed off."
One recent acquisition of a work by the little-known 15th-century artist Hans Wertinger was a "bummer" without "a millimetre of original observation or feeling".
He says the decision to allow the Tate Modern to tell the story of art from 1900 means that the National does not tell a coherent story. It handed Monet's Water-Lilies to the Tate Modern because it was painted after 1900.
Mr Spalding says: "The National Gallery has no Matisse, no Picasso. How can it hope to tell the continuing story of art?
"Tate Modern is designed for showing installations. Paintings, particularly older ones, often look miserable and out of place there."
Mr Spalding, who recently questioned the direction of the National Gallery in the New Statesman magazine, concludes in his book: "With Tate Modern assuming the role of our national gallery of the 20th century ... the whole National Gallery could, in time, become crowded with minor works that could help explain the context of the great masterpieces, but could also dilute their power. Recent purchases at the National Gallery suggest that this has already begun to happen."
Mr MacGregor was quick to defend himself. He said: "The National Gallery exists to do two things: to collect and present great works of art and to enable the visitor to discover the story of European painting. It is by these criteria that all we do must be judged." Sir Nicholas was not available for comment. He also came under fire last week when it was announced that the Tate's long-serving director of collections, Jeremy Lewison, had become the latest senior employee to quit.
Mr Spalding also argues in his book that "museums are riven with internal disputes like a spider with a brain in each leg, straddled by impotent directors and prey to opinionated boards".
He proposes museums pool collections to improve public displays and research.
And he envisages a fictional visit to the British Museum 10 years hence, when there would be a tailor-made exhibit for each visitor, hands-on programmes, on-the-spot research possibilities and individual presentation of objects for different age groups, interests and spans of attention.Reuse content