In the rush to cash in, councils illegally granted planning permission that is now being revoked.

"One Sunday morning we opened the newspapers, and there it was - a double-page photograph of our building, saying it was going to be demolished," says Marisa Toomey whose retirement home is one of those affected.

It pains her to recall the saga of Banana Beach, a plush seaside development in Marbella, under threat of demolition by Andalucia's provincial government.

Mrs Toomey, who is Spanish, bought an apartment there in 2004 with her British husband John, a retired property lawyer from London.

'Devastated'

"The documents were drawn up by two Spanish solicitors and verified by an independent notary," stresses John Toomey, producing a wad of paperwork to confirm the apparent legality of the purchase.

Only later would the couple learn that the site should never have been approved for residential use.

"We bought in good faith," explains Mr Toomey, "and we're devastated. It could not possibly happen in England - everything was totally legal and subsequently it was made illegal."

Banana Beach was one of dozens of big money construction projects approved in the 1990s.

And Marbella, in turn, is just one symptom of a development malaise which has stricken the Spanish costas.

Coastal regions represent just 7% of Spain's territory and yet are home to 44% of the population.

In some communities, three-quarters of all land adjoining the coast has been urbanised, and much of the infrastructure is geared towards the 48 million tourists who annually spread their towels on Spanish sand.

"The last decade has seen the same number of new buildings as in the whole of our previous history," explains Maria Jose Caballero of Greenpeace.

"For years, people have thought they can build wherever they want along the coasts. We need to change that mentality"

Spain's left-wing government agrees, and boasts that 665 illegal structures have already been bulldozed this year.

Technically, any property built close to a beach after 1988 could be ripe for demolition; while thousands more buildings fall foul of local and provincial planning laws, including Banana Beach in Marbella.

Madrid wants the regions and town halls to sign up to a nationwide development strategy, costing an estimated 5 billion Euros.

Unable to sell their apartment because of the threatened demolition, and sceptical about any promise of compensation, John and Marisa Toomey are already counting the cost of an ill-fated investment.

"This was for our retirement, these were our savings. It's very sad," says John, with British understatement.

His Spanish wife puts it more bluntly: "Our lawyers in Spain have said the compensation will take years and years. We'll probably be dead by the time anyone decides to compensate us."