Madrid - Santa Coloma de Gramenet, Barcelona, Castro de Rei, El Ejido, Valencia, Madrid, Majorca...

The list of Spanish towns and cities enmeshed in corruption scandals seems endless, with new cases emerging almost daily.

"Corruption scandals have tarnished all the political parties, spreading all over Spain during the last decade," the daily El Mundo observed in an editorial.

Many observers regard corruption as a growing threat to Spain's democracy, while others take a more optimistic view, seeing the increase of corruption revelations as a sign that there is a crackdown on corrupt politicians and entrepreneurs.

Political corruption has cost Spain more than 4 billion euros (6 billion dollars) in kickbacks or inflated public contracts over the past decade, El Mundo said, basing its calculation on ongoing judicial proceedings.

The real cost of corruption was likely to be much higher, according to the daily.

Corruption is constantly making headlines, with around 60 business figures or politicians having been named official suspects in a wide corruption network involving the main opposition conservative People's Party (PP).

The suspects include a PP treasurer and a European legislator who have resigned over the case.

Most recently, the jailed mayor of Santa Coloma de Gramenet near Barcelona stepped down over corruption charges, while an investigation was launched into the alleged embezzlement of up to 20 million euros at a Barcelona auditorium.

More than 120 officials belonging to the PP and Prime Minister Jose Luis Rodriguez Zapatero's Socialist Party - mainly mayors and local councillors - have been named suspects in corruption cases over the past five years, according to a figure quoted by the daily El Pais.

Spain's decade-long construction boom is seen as having provided one of the main feeding grounds for corruption.

Municipalities short of funds have used building licences as one of their main sources of income, a situation which has encouraged backhanders and illicit practices.

Around 20 acting mayors have been detained on corruption charges linked with urban planning since 2006, when the entire city council of Marbella was dissolved for massive corruption involving illegal building permits.

The housing boom finally evaporated as a recession kicked in last year.

Corruption has meanwhile risen to be one of the problems that most worry Spaniards - above Basque terrorism or the quality of the health care - according to several recent polls.

The lack of sufficient controls contributes to "an impression that acting correctly, doing things well, seeking excellence is (a sign of) stupidity and naivety," as Ethics Professor Francesc Torralba described the prevailing mentality.

Democracy was seen by corrupt politicians as a mere "instrument to satisfy personal ambitions" and to get rich without effort, El Pais complained.

Corruption "is not only threatening to ruin the reputation of politics ... but also citizens' indispensable trust in the institutions," the daily said.

On the other hand, the increase of corruption revelations reflects growing criticism of such practices, Jesus Sanchez Lambas says.

The lawyer is associated with the corruption research organization Transparency International, in whose index Spain has fallen from the 22th to the 28th place among a total of 180 countries since 2004.

"Although unfortunately, Spain is not among the Nordic countries, which are the least corrupt, the cases we are seeing now result from ... more intensive work" against corruption by the judiciary and police, Sanchez Lambas told the German Press Agency dpa.

Reactive measures, however, are not sufficient to uproot "this cancer which is ... as old as humanity itself," political science professor Victor Lapuente said.

The governing Socialists and the opposition conservatives are now considering new measures to fight corruption.

The measures under consideration include half a dozen legal reforms in areas including the financing of municipalities and political parties, reports said. (dpa)