European and La Liga champions Barca and great rivals Real, the world's richest clubs in terms of revenue, take about half the total pot of TV income of 600 million euros, allowing them to buy the best players and pay exorbitant wages.
The remaining 18 teams earn far less than their peers in rival European leagues, where a system of collective bargaining allows for fairer revenue distribution, and have no chance of challenging for the title.
Seville-based Betis, one of Spain's best-supported teams, have slipped deep into the red just like many other clubs as they strive to remain competitive. They have also been forced to seek court protection from their creditors.
"As we have seen the last few years there are only two teams that have a chance of winning La Liga," Betis president Miguel Guillen told Reuters in an interview held in his modest office on Tuesday.
"The gap between Barcelona and Real Madrid and the rest is going to get bigger and bigger," added the 42-year-old business administration graduate.
"This is doing great damage not only to the other clubs that are not Real Madrid and Barcelona but also to our league.
"In the long term we are hurting our league because there will be less interest and it will generate less TV revenue."
Guillen is the latest president to call for change in the distribution of Spain's TV money and the introduction of a system similar to the one used in the English Premier League.
Jose Maria del Nido, president of Betis's city rivals Sevilla, said this month that the Spanish league was "third world" and "a load of rubbish."
An agreement Barca and Real brokered last year with 11 other top-flight sides on sharing some of the TV cash from 2015 is likely to cement their advantage while helping the other clubs only marginally, analysts have said.
Figures collated by Jose Maria Gay, a professor of accounting at the University of Barcelona, show Barca earned 158 million euros from their TV deal in the 2009-10 season, or 26 percent of the total, and Real 136 million euros, or 22 percent.
Real's city rivals Getafe, 2008 UEFA Cup quarter-finalists, earned six million, or one percent.
In the English Premier League, Manchester United made 64.5 million euros from domestic TV rights in 2009-10, 5.8 percent of the total.
Smaller clubs like Wolverhampton Wanderers (43.8 million) and Wigan Athletic (42.8 million) were allocated about four percent of the pie.
"We do think [the Spanish system] needs to be changed," said Guillen who has been tasked by Betis administrators with getting the club's finances back in order after years of mismanagement.
"Considering that it's such an important part of income, the distribution needs to be more equal between the clubs.
"People in South America, in Asia, in the United States, are going to lose interest because they know there is nothing much outside the matches bet
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