The demonstrators, representing some 30 ecological groups, claimed that some of Spain’s most important national parks and historic areas had been blighted since planning powers were handed from central government to often corrupt local authorities.

The unprecedented demand for holiday homes from northern Europeans, particularly Britons, had fuelled the development, protesters said.

“Construction is ruining the environment in Spain,” Ramón López de Lucio, an architect and Professor of Urban Planning at Madrid University, told the protest meeting.

He added: “In Madrid there are 300,000 empty apartments but speculative construction is going on further and further away from the city. During the past decade, aggressive construction has increased 50 per cent in Madrid and on the Costas.”

Statistics released last week showed that 1.6 million home units were currently under construction in Spain. Last year 757,680 flats were built in the country, more than the total number built in France, Italy and Germany together.

Ciudadanos Europeos, a foreigners’ organisation on the Costa Blanca, estimates that 100,000 holiday homes have been built in Spain each year for the past six years.

Britons easily outnumber other nationalities as the main buyers, especially since the advent of cheap flights. Now 1.3 million homes in Spain are owned by Britons, who made more than 18 million visits to Spain last year. Many corrupt local councillors are in cahoots with developers, allowing building in areas that should be protected, such as national parks or around historic monuments.

A spokeswoman for the Environment Ministry in Madrid admitted to The Times that the situation was out of control, but said that efforts were belatedly being made to amend the relevant legislation.

Many of the demonstrators in Madrid were from San Lorenzo de El Escorial, 40 miles northwest of the capital. The town’s mayor faces several corruption charges for allowing illegal construction that destroyed the setting of the Escorial monastery-palace, a Unesco World Heritage Site.

Spain had promised Unesco that it would preserve the massive historical edifice, built by Philip II in the 16th century.

“Escorial and the landscape around has been ruined,” said Michael Harris, a British author of English textbooks who is an Escorial resident and vice-president of Entorno Escorial, an action group.

• More than 35,000 people, including politicians, marched in the Basque city of Bilbao on Saturday as nationalist radicals voiced anger at a perceived campaign by Spanish authorities to curtail their civil rights.

  The marchers, from groups sympathetic to the Basque nationalist cause, said they were unhappy with judicial investigations that they claimed restricted their rights and treated them as potential terrorists.

  Judge Baltasar Garzón has waged a campaign against the separatist group Eta and has been examining groupings seen as sympathetic to it, such as the banned hardline nationalist party Batasuna. (AFP)

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