Will Brighton's Modernist marvel sink without trace?

In 1937, at the height of the German-inspired fashion for open air bathing, Richard Jones opened his streamlined Saltdean Lido near Brighton. It remains the outstanding example of Marine Modernist architecture in Britain.

However, its condition has gradually deteriorated since 1997, when Brighton and Hove City Council assigned a 150-year lease to accountant and leisure sector businessman Dennis Audley, and the pool could meet the wrecking ball as part of plans to redevelop the site with flats.

Sir Terence Conran's architecture firm has joined the increasingly messy fight to save Saltdean Lido.

Sir Terence said: "I find it quite disgraceful that the lido has been left to rot. We must find ways to preserve our architectural heritage and breathe new life in to beautiful old buildings."

A key precedent looms. If Saltdean, of all lidos, is redeveloped clumsily, it may trigger a laissez-faire approach that could see most of Britain's 50-odd Modernist lidos facing architectural ruin.

Campaigners hope to persuade the council, which owns the lido, to take back the lease from Mr Audley and let them run the grade II-listed baths on a not-for-profit basis. The Save Saltdean Lido campaign has generated 7,000 supporters on Facebook, staged public meetings and asked English Heritage to request Grade II* listing. The influential 20th Century Society supports that move.

This isn't just a Punch and Judy show five miles east of Brighton – supposedly venal developer versus frightfully concerned local worthies. There is something implicitly feckless about it all. There are 400,000 people in the Brighton and Hove conurbation, many of them well-heeled and style-conscious.

Yet Mr Audley's architect, Mark Strawbridge, claimed that the council's leisure services department had told him that nobody used the lido – and that the council didn't need an outdoor pool. He also described Conran and Partners as "gross opportunists".

The architect said that Mr Audley's original 102-apartment scheme for the lido had been deliberately provocative in the face of council indecision. (It was duly blocked by local opposition.)

Mr Strawbridge's new design, likely to be submitted in September would restore the lido's key features, create a new indoor pool, and an off-site library and community centre. The scheme features roof gardens and solar power technology. He insisted that the poor condition of the lido was the result of pre-lease council repairs which had sealed in concrete-rotting moisture. And he said that Mr Audley would strongly contest a recent statutory repair notice served by the council. "Lidos have to be subsidised," he added.

The ghost of Hans Uren, Prussian author of the 1924 bestseller Man and Sunlight, must be glaring down in disbelief from Valhalla at the decayed concrete of Saltdean Lido. "Greetings to you, you who are sun lovers!" he wrote. "You bear ardent longings in your hearts! Longings after warm sunshine, blue skies, light and nature, victorious strength, spiritual loftiness and childlike faith."

What has happened to those ardent longings? Why are historically significant lidos such as Tinside Lido at Plymouth struggling to remain viable, despite a £3m makeover? It's the same story at the magnificent Jubilee Pool, Penzance, which is "limping on" according to Jon Wright of the 20th Century Society. Is lido water simply too cold for 21st-century bathers?

Broomhill Pool at Ipswich is a salutary example of the situation facing many lidos. Icelandic bank fal-out and new public sector cutbacks at the local authority killed a previously ring-fenced £1m to support modernisation proposals co-drafted by the Broomhill Pool Trust and Fusion Lifestyle – the latter have already turned lidos at Brockhurst Park and Uxbridge into going concerns. Yet if Ipswich Council is forced to privatise its leisure facilities, Broomhill Pool could still be saved as part of a private operator's rescue deal, said the Trust's spokesman, Mike Cook.

Conran and Partners is working free of charge with the Save Saltdean Lido Campaign to draw up alternative plans to make the site viable, without touching the elegantly designed ensemble of its pool, sun deck, curved wings, raised terrace and cafe. Conran's project architect Paul Zara has already successfully refurbished another equally iconic local building from the 1930s, Embassy Court in Hove.