Do we all dream of life in a garden city? Mrs Thatcher, however, put an end to the new towns - council housing, too - and since then, under New Labour and Coalition governments, we are supposed to have enjoyed an "urban renaissance," along with eco-towns, the Thames Gateway and the positively insane Pathfinder project, whereby streets of perfectly good 19th-century homes in Liverpool and Manchester have been demolished for no discernible reason. One way or another, all of these initiatives have been failures: New Labour's "urban renaissance" descended, year-by-year, into a new Dark Age of rampant, uncivil property development; while eco-towns - a New Labour joke - were too environmentally unfriendly to win friends except among the foxiest property speculators. The idea of 21st-century garden cities might sound appealing - a government-backed quintessence of rus in urbe (or urbe in rus) planning - yet the whole point of garden cities is that they were small. Far from wanting us to think big, Ebenezer Howard imagined his ideal new cities supporting populations of no more than 30,000. Given over in almost equal proportions to industry, agriculture and residential areas, these would be small enough to walk to work in and, wherever possible, self-sufficient. Given that, according to Mr Clegg, there will be 2.3 million new households over the next 10 years, an increase in population of perhaps five million people, we will need more than 150 new garden cities - or 10 new cities, with or without gardens, the size of Liverpool or Manchester. Put this way, the latest government housing initiative seems absurd, its recommendations defied by simple mathematics. In reality, many of these future households will take root in existing towns and cities, while most people, however poor, will gravitate to London and the South East - a fact that, by itself, highlights one of the greatest difficulties of building new garden cities. Old or new, towns are shaped first and foremost by their economies, by trade and manufacturing, by what they do. There is absolutely no point in building new towns if their primary purpose is to meet a housing shortage. Households need jobs, and a city is built around these. Imagine if a garden city had been decreed close to Swindon in the 1820s. Few would have been tempted to settle there. But when the Great Western Railway opened its famous works in 1841, people flocked there to find jobs; this small market town grew, and continues to thrive, because it built locomotives, just as Barrow-in-Furness has long spelt submarines, Northampton shoes, Nottingham lace and Melton Mowbray pork pies, while London has long been a world-in-a-city, a New Rome, founded, of course, by the Romans themselves. Through these economic activities, British towns gained their special characters. Neither the garden cities nor new towns have matched them, even though Ebenezer Howard adopted the core ideas underpinning them, on a tide of soapsuds and a rush of chocolate, from idealistic 19th-century industrial "villages" - notably, Port Sunlight, built by the Lever Brothers; Bourneville, by George Cadbury; and New Earswick, by Joseph Rowntree. Letchworth was better known for smocks and calisthenics, its open-air school for theosophical meditation, and for its first pub, The Skittles, where alcohol was prohibited, than for its industry. Walter Wilkinson, the Punch satirist, was moved to verse: Now what did they want with a milk-and-water pub When milk shops they were rich in? Come on, boss! Let's go and have a drink! We can get one down in "Itchin. If garden cities were seen as arty-crafty, middle class, and the antithesis of heavy-duty manufacturing towns such as Crewe and Swindon, the new towns were a fanfare for the common man, woman and booming baby. Even then, culture was imposed on them from above by well-meaning architects, planners and mandarins. What could have been more agreeable than to have watched Sir Kenneth Clark, garbed in a beautifully bespoke suit, unveil Henry Moore's Harlow Family Group in the town of that name one day in 1956? Why, just eight years earlier, Lewis Silkin, Clem Attlee's minister of town and country planning, had told local people shortly before work began elsewhere in Essex: "Basildon will become a city which people from all over the world will want to visit." Perhaps it is; and yet, for the most part, garden cities and new towns have become dormitory suburbs of London. Milton Keynes might boast that over half of those who work there commute locally, yet very many rush up to town - meaning London - by train each day. It seems somehow significant that far away, across the South Atlantic and over the distant red planalto central of Brazil, politicians and civil servants are always first in the queue at the airport to join Friday evening flights from Brasilia, the new federal capital with its garden city plan inaugurated in 1960, to the sheer exuberance of Rio de Janeiro, a seaside city founded 400 years earlier, ever more crowded and open to the world. No one doubts that we need new homes in Britain yet, for all their theoretical appeal, garden cities and their progeny are not the answer. We need to create or attract new industry, new jobs up and down the country and wrap new homes around them. Then, new towns and cities with a purpose, a culture and an identity will emerge, offering a genuine and truly viable alternative to our hard-pressed old towns and old cities that, meanwhile, we will continue to stretch, patch and grudgingly nurture.