"In 2004, the government set up a special contributions regime for people coming to work in our country and who establish their fiscal residence there," Cinco Dias reported.

The ruling was dubbed "Beckham's Law" as it was applied just months after England star David Beckham arrived at Real Madrid and allowed a Spanish club to pay out less than English, German, Italian and French counterparts to foreign players in salary-related costs.

"On the basis of the same net annual salary a Spanish club pays around 29 percent less than Chelsea, 32.5 percent less than Inter Milan and 26 percent less than Bayern Munich in terms of gross salary," the study shows.

Adding to the advantages the foreign players enjoy over other countries are the smaller social charges they generally pay to the Spanish treasury.

A player on a net salary of two million euros -- top players such as Beckham and Ronaldinho earn around three times as much -- would cost a French club a total package of 5.4 million euros, compared with around four million for an Italian club, 3.8 million for an English club, 3.6 for a German club and only around 2.7 million for a Spanish outfit.

France Football magazine recently reported that Ronaldinho and Beckham were this season the two best-paid players in the world.

Spain has in recent years splashed the cash on players and for the just-ended 2006-2007 league season La Liga clubs shelled out more than 300 million euros on signing new players.