Will Bath lose its World Heritage status?

Only two cities on the planet are World Heritage sites. While it's true that parts of other cities have the cherished status, in just two cases does the designation apply to the whole place. One of them is Venice. The other is Bath.

The ancient spa town, a source not just of hot, healing waters but of undiluted architectural wonders, picked up the Unesco honour 22 years ago. Although Bath is famed for the magnificent Royal Crescent and its glorious adjoining Circus, the city's Georgian squares and crescents are all exquisitely proportioned and lined with handsomely crafted buildings, rising gently up a beautiful basin in the green Somerset landscape. The fact that so many people continue to live in the city centre is a credit to 18th-century speculators and architects, who transformed a quiet medieval town into one of the most fashionable and best-looking cities of its age.

Now, though, Bath risks being stripped of its status, a fate that has so far only befallen the Arabian Oryx Sanctuary in Oman, which was scrubbed off the list two years ago for dramatically reducing the size of its protected area. So what has made Bath a concern for Unesco? Why did its inspectors visit the city last autumn?

When you step out of the railway station, designed by Isambard Kingdom Brunel, pretty much the first thing you see is a vulgar new shopping mall, dolled up in a style you might call Las Vegas Georgian for its soulless imitation. This is SouthGate, designed by Chapman Taylor, an architecture firm specialising in city-centre malls. SouthGate's new shops, which will give Bath a glut of the kind of chain stores and cafes you can find in any British city, are basically bulky concrete boxes pasted over with little more than a veneer of Bath stone. While these faux-Georgian frocks might look convincing in computer drawings, in reality the effect is crude and deeply disappointing. Georgian architecture, even when rushed up, was always beautifully proportioned and lovingly detailed by craftsmen.

How SouthGate's clunking buildings got planning permission would be a good question if we didn't already know the answer - it looked, in pre-recession days, like a strong commercial proposition, and would be faced with local, honey-coloured limestone, however mean the cut. But SouthGate's biggest crime, perhaps, is that it gets wrong what the rest of Bath gets so beautifully right: proportion. It's just too big. It can't fit in.

In 1942, German air raids on Bath killed 400 people, destroyed 900 Georgian buildings, and damaged a further 12,500. Yet thoughtless postwar development harmed the fabric of the city far more. Swaths of what survived of Georgian Bath were destroyed by local authorities, big business and architects, until Unesco finally stepped in to protect it in 1987.

Were its inspectors, who had been alerted to the poor quality of the latest building projects, as shocked as I was by Bath in the present day? We'll know in June, when their report is presented to the World Heritage committee. But as I strolled around the city, which earns much of its living off the back of its heritage status, I couldn't help wondering if the council leaders really cared about losing it.

How else could you explain planning permission being granted for Western Riverside, a thumping great residential proposal the size of 19 football pitches that will boast 2,200 flats? At the heart of the scheme, set on the site of a derelict gasworks, is a grid of new streets lined with blocks of nine-storey flats, of a kind you might find anywhere from Berlin to Beijing. The regimented layout and the stiff, drab design of the buildings are in stark contrast to the lilting ebb and flow of the rest of the city. As a sweetener, the developers, Crest Nicholson, have offered Bath an "ecology park" - a public place with grass, trees, flowers, insects and birds. Not much different, in fact, from what we used to know as a "park".

Western Riverside's architects are Feilden Clegg and Bradley, part of the team responsible for the award-winning Accordia housing scheme in Cambridge. In Bath, though, the architects have been unable to come up with such a convincing modern scheme. Like SouthGate, which is expected to be completed next year, Western Riverside lacks a sense of both scale and place. Georgian Bath is an elegant jumble of shops, houses, pubs and public buildings. Western Riverside is just blocks of flats and shops.

From the outset, it faced opposition. The International Council on Monuments and Sites is a body that advises Unesco. Susan Denyer, ICOMOS's UK representative, wrote to Bath and North East Somerset Council last year, warning that approving the scheme could jeopardise Bath's status. "We urge the council to reject this application," she said.

But the council did the opposite. "There is no statutory protection for World Heritage sites in UK law," explains Caroline Kay, chief executive of Bath Preservation Trust, which contested the proposals. "Bath is at the mercy of developers driven by commercial interests."

The Trust, which can only advise the council, went along with the SouthGate proposals, hoping they would turn out more Georgian than Georgian theme park. It now regrets this decision, and has come out heavily against Western Riverside - unlike central government. Before Unesco met to discuss sending in inspectors, Peter Marsden, of the Department of Culture, Media and Sport, wrote to the organisation, pointing out that the development was "outside the parts of the World Heritage site containing the Roman archaeology, Georgian town-planning and Georgian architecture"; nor would it intrude upon "any important views from the historic parts of the city".

But cities are organisms. It is wrong to see one bit as "historic" and another as "new" without understanding that the two are joined. The experience of Bath as a whole has been damaged. SouthGate is just a few minutes' walk from Bath Abbey, while Western Riverside's site on the city's fringes could be as beautiful, in its own contemporary way, as the Georgian sections.

Getting something new, worthwhile and special built in Bath is tricky. James Dyson, the inventor and vacuum cleaner magnate, recently wasted £3.5m in a long, drawn-out bid to get a college of design innovation built within the Victorian walls of an old craneworks on the banks of the Avon. Here, students would have learned how to create and engineer rather than merely shop. The plans, by Wilkinson Eyre, married a futuristic superstructure to the old factory, while retaining its Grade II-listed facade. Late last year, however, the project was abandoned after it failed to get government funding, the Environment Agency having voiced fears of flooding (this does make you wonder how Western Riverside, which is nearby, was ever approved).

Dyson vowed "to find another way to nurture young engineers - this time on our own terms". He is now funding a building for the Royal College of Art in London, where design and engineering will be taught. Bath's loss is the capital's gain.

Meanwhile, after much heated debate, Eric Parry's controversial, ceramic-clad extension to Bath's Holburne Museum has been given the go-ahead, and the reserved blessing of local conservationists keen to see something fresh in the city, especially now Dyson has gone. Not that Parry had things all his own way. The cladding of the building was to have been blue, a colour too far for conservationists. The agreed choice? You guessed it. A shade resembling Bath stone.

The most strikingly modern building in the city, the new Thermae Bath Spa complex, which opened three years late and went way over budget, is a fine creation only the churlish could fault. Its rooftop pool allows you to swim in glorious, naturally hot water. This really is special. I splashed there happily, looking out over spires and rooftops to the green belt beyond. Luckily, the steam obscured SouthGate, although that green belt is currently threatened by proposals for thousands of bland new homes, making a tough Unesco report all the more urgent.

The recession may yet kill off Western Riverside. But we will have to wait till June to see if Unesco has the sense, and courage, to condemn Bath for trying to destroy itself. The tragedy is that it could do so much better for its citizens - and all those tourists who come to marvel at a spa town that, for now anyway, is ranked alongside Venice.