PUCCINI opens La Bohème in an attic where Rodolfo tosses his new play on to the fire for warmth and Marcello sobs before his painting of The Red Sea: “Its waters have run cold.” This 110-year old view of the life of the artist is alive and well in 10 Downing Street.

Just before Christmas Tony Blair succumbed to tears and a bleeding heart and agreed that, from next month, all artists whose work changes hands on the market for more €1,000 or £680 will receive 4 per cent of the price to warm their tiny hands. On £680 that’s a princely £20.40, after admin. As moral gestures go, it is a winner. As the mother of all disasters for sales of art in the UK, it is also a winner. But what is good government against a twang on the heartstrings?

The tax supposed to benefit the struggling artist in his garret is the notorious European droit de suite — a French invention of the hard-up 1920s which, like many handouts from hard times, has survived into the 21st century. Its damage is of two kinds. Art that is taxed simply goes elsewhere. Worse, droit de suite over 80 years has put millions in the pockets of the rich such as Picasso and Matisse, but left the impoverished as poor as before.

Artists need dealers to sell on their work. Mr Blair, in a response to the touchy-feely lobby, has increased the burden on dealers and auction houses by dramatically lowering the sale price on which they must collect and refund droit de suite.

The burden is not just 25 lines of form-filling. It is hours of confusion. Dealers must look up directories to establish if a Polaroid or a Wedgwood tea pot are “works of art”. They must find out if the artist, if not European, is a national of a “reciprocating” droit de suite country (including Burkina Faso).

Marcello in his attic can now expect his dealer to stare at low-priced art and ask: is this nightmare worth the trouble?

“If you ask me to choose between making one sale at €10,000 or ten at €1,000, I have no choice,” says Patrizia Papachristidis, who brings Italian painters and photographers to the West End. “Why should I vote for all that hassle?”

This, says Anthony Browne, chairman of the British Art Market Federation, not usually driven to extremism, is “absolutely absurd”. Mr Blair has one month to avoid the law of unintended consequences and withdraw this change — or hugely reduce the dealers who sell the humble artist.