Madrid, who won the Spanish league last May for the 32nd time, became the first club in any sport to generate more than 500 million euros ($664 million)in annual revenues, Deloitte said in its annual Football Money League for 2011-12.

The perennial Spanish rivals retain loyal domestic support, attracting crowds in excess of 80,000 despite Spain's recession and high unemployment. A global fan base also helps them to sign up lucrative international sponsorship deals.

The Spanish duo have the advantage of doing their own television deals rather than selling collectively through a league as their main European rivals do. The downside is that it has added to a polarisation in Spanish soccer where many other clubs are struggling to stay afloat.

England's Manchester United were in third spot behind the Spanish duo despite a fallow season in which they failed to win a trophy for the first time since 2005.

Germany's Bayern Munich were fourth, followed by Champions League winners Chelsea and Premier League rivals Arsenal.

"An unchanged top six emphasises the fact that these clubs have some of the largest fanbases and hence strongest revenues, in both domestic and international markets," said Dan Jones, a partner in the sports business group at Deloitte.

The growing commercialisation of soccer has led to a debate about whether the people's game has become too expensive for fans and clubs have lost touch with their local communities as they chase revenues around the globe.

Big-spending clubs face pressure to boost revenues to avoid falling foul of rules being introduced by UEFA, European soccer's governing body, which mean they must move towards breakeven or risk exclusion from top continental competitions.

EUROPE'S BIG FIVE LEAGUES

In total, the earnings of the 20 clubs rose 10 percent to 4.8 billion euros in 2011-12, underlining how top European teams are still commanding big fees from pay TV companies and corporate sponsors despite a tough economic climate.

The leading 20 clubs accounted for more than a quarter of all revenues in the European soccer market, illustrating the gulf between rich and poor in the sport.

Deloitte reviews soccer clubs around the globe but all the clubs in the top 20 were drawn from just five European leagues. England's Premier League, the world's richest thanks to its domestic and international TV deals, is home to seven of the 20.

AC Milan, owned by former Italian Prime Minister Silvio Berlusconi, were the highest ranked of five Italian clubs, while Germany supplied four teams and France two.

English champions Manchester City, bankrolled by cash from Abu Dhabi, showed the strongest revenue growth after winning the English league for the first time in 44 years. City's earnings were bolstered by an enhanced sponsorship agreement with Etihad Airways.

Despite their higher revenues, City still lost almost 100 million pounds ($159 million) last season.