Should the state pay pounds 3/4m for this?

No: Private patrons ought to fork out

Art is the name of an excellent new play in London's West End. Its real star is an enormous all-white canvas, supposedly white lines on a white background, though of course these are impossible to see.

The arguments that ensue over the intrinsic worth or otherwise of this (highly expensive) painting are among the sort of arguments the Heritage Lottery Fund wants to avoid in its 20-year rule.

Much that is acclaimed but controversial, much that is rubbish but acclaimed is admittedly more than 20 years old. But at least a couple of decades should see a weeding out of most of the fashion-chasing media darling artists, the hyped pictures and faddish movements.

A 20-year rule, argued the fund trustees under Lord Rothschild when the lottery rules were being drawn up, was a reasonable time in which to assess the artist's significance and the significance of the work itself.

Lord Rothschild said last night: "It seemed a reasonable period of time to get a balance and focus about what would become heritage. We were even nervous about as small a period as 20 years. Certainly, it should also apply to great painters of the day. Painters can change a great deal in their lifetimes, and later work is not always consistent with their great years, though as it happens Lucian Freud is at the height of his powers as a painter. A period of reflection can only be helpful."

Much has been made in the last few years about trends in "video art" and in the New York contemporary art scene. But Robert Hughes, the notable art critic whose retrospective series American Visions is about to be shown on BBC television, told me: "I don't now think there is any video art of lasting worth and American art at present is in the doldrums."

In the visual arts, perhaps more than any other art form, reputations rise and fall in a remarkably short time. In comparison, 20 years is an age.

In addition, private benefactors such as the advertising mogul Maurice Saatchi have in the past stepped in to buy works by leading names, though these names are often of a more avant-garde persuasion than the figurative painter Lucian Freud. There is indeed a continuing danger that we will lose works of art to America, and it is no coincidence that Lucian Freud's dealer is now Aquavella of New York.

But if one of these quangos needs to change its rules, it is the Arts Council, which should be allowed to use lottery money to gamble on contemporary art, and not the Heritage Lottery Fund. Freud may be part of our artistic heritage, but that does not mean that his newest works are necessarily among his best. If heritage is to have any meaning, it must be that a created work cannot be considered part of the cultural heritage until it has achieved either critical or public acclaim over a long period, transcending fads and fashions.

Even David Barrie, the campaigning director of the National Art Collections Fund, which has given pounds 75,000 towards keeping the Freud painting in the country, and is frustrated with the confusion over lottery funding by Heritage and Arts Council funding bodies, is prepared to defend the 20- year rule.

"Contemporary art is a very tricky area," he says. "It often takes a little time to establish whether a work of art is going to establish heritage status. That's particularly true with avant-garde work, Damien Hirst for example. But Freud is a living classic. One knows his work will be part of the heritage very soon.

"What we need is for the Heritage Lottery Fund to have a 20-year rule but have the courage to make exceptions to it for contemporary works of outstanding quality."