BOB GELDOF is not the only superannuated rocker whose political gifts overshadow his more limited musical contributions to recent cultural progress. Sonny Bono, too, is a name currently buzzing through the Culture Department’s chill-pad in Cockspur Street, even though Bono departed his California stage set seven years ago. His biggest hit, you may recall, was the audaciously self-serving law he championed that extended United States copyright protection by 20 years. Worryingly, it is a tune that our own Culture Minister, James Purnell, appears unable to clear from his head.

Mr Purnell, who is in charge of our “creative industries”, believes that we, too, need to “modernise our intellectual property framework” along similar lines. Following a music industry campaign to extend the copyright term for sound recordings from 50 to 95 years, he has been rapping in rhythm with the EMI and BMG massive: in a risky, talent-driven business like pop, the suits, apparently, need guarantees of long-term financial returns. As he told the Institute for Public Policy Research yesterday, the record labels need copyright reforms “that will allow them to make returns on their creativity and to invest in innovation”. What he failed to explain was the damage that such a short-term corporate grab would do to the public good.

Copyright has always been a delicate compromise between the needs of artistic creators and the cultural richness of a wider public domain. Our first such law, the 1710 Statute of Anne, “for the Encouragement of Learned Men to Compose and Write useful Books”, limited protection to 14 years, extendable for a further 14. Authors were expected to have ample time to exploit their works within such a term. Over the years, the time period was gradually extended — to 50 years after death in 1956 — but the principle remained unchanged: copyright was never simply a right for publishers to maximise their investment.

The music business, in the guise of the International Federation of the Phonographic Industry (IFPI), has decided otherwise. The IFPI claims that the “huge disparity” in copyright terms with the US makes it “hard to do business” here — funnily enough, Bono used the same argument when the old US system offered less protection than in Europe. You may have heard its heartfelt appeals for social justice: Kenney Jones, of The Who, protesting that extended royalties could usefully pay the school fees; Sir Cliff Richard, furious to be deprived of income “simply because I have outlived the copyright on my sound recordings”.

Please don’t tease. Such half-baked arguments owe more to the short-term financial pressures facing the perma-tanned hipsters running the record labels. They are wilfully ignoring the vital creative role of the public domain in reinvigorating our common culture. Had they been genuinely innovative over the past decade — beyond discovering Crazy Frog and “girl power” — the moguls would have noticed that their industry’s greatest injections of energy have originated not within their own well-cushioned empires but in the public domain. Remember their aversion to MP3 downloads, now a vast corporate revenue stream? Or the copyright-breaching “mash-ups” — unauthorised combinations of existing music samples mixed by DJs — that first attracted music industry writs, and then were worked into Kylie’s routine?

Digital technologies are merely amplifying the historic tendency towards mixing and sampling that has shaped works from Macbeth to Mickey Mouse. Once creative works are in the public domain, people frequently make wonderful new things with them — a process denied by the encroachment of corporate interests through copyright extensions. Would West Side Story have been made if Shakespeare’s heirs could protect Romeo and Juliet? Would Frank Capra ’s It’s A Wonderful Life have been reinvented as a Christmas TV classic had it not slipped out of copyright in 1975 and been rediscovered by a new generation who could buy it cheaply on VHS?

By extending the protection term, would artists be encouraged to be any more creative? It is unlikely that Sir Cliff would have sung Summer Holiday less perkily if he had known it would have benefited him for only 50 rather than 95 years. And what of the Joyces and Plaths, whose controlling families could use ever longer extensions to suppress material at whim?

There are also the interests of lesser-known artists to consider. A blanket copyright extension would encourage record companies to restrict access to their entire back catalogues, even works (the vast majority) that they would never exploit. Yet freely available, on other labels’ cheap CD collections, otherwise forgotten performers could discover new life. In that odd way in which markets work, the benefits of such cultural entrepreneurial drive could accrue to the original owner of the rights.

The essayist and historian Thomas Babington Macaulay understood the perils when a similar battle to extend copyright was being waged in 1841. Amid calls to stretch the protection to 60 years after death, Macaulay saw no public benefit from a monopoly lasting longer than 42 years or life. “Are we free to legislate for the public good, or are we not?” he asked in the House of Commons. “Is this a question of expediency, or is it a question of right? An advantage that is to be enjoyed more than half a century after we are dead, by somebody utterly unconnected with us, is really no motive at all to action.” Many valuable works, he argued, would be suppressed — and publishers treated with such contempt that the reading public would happily turn to “piratical booksellers”.

A 20-year patent limit forces other industries to innovate, so why should the innately risk-averse record labels need any more than a 50-year monopoly? If Mr Purnell truly wants to foster creativity, he ought to broaden his musical tastes.

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