- UEFA withholds payment of prize money to 23 clubs
- Clubs punished for owing money to other teams, employees or failing to pay taxes
- Europa League and European Super Cup winners Atletico is one of the 23 clubs to be punished
- Payment of prize money will be withheld until the clubs have paid the money owing
Some of Europe's leading clubs -- including Europa League and European Super Cup winners Atletico Madrid of Spain -- have had a taste of just seriously UEFA is taking the idea of Financial Fair Play after the European governing body temporarily withheld the payment of prize money to 23 clubs.
UEFA Club Financial Control Body's investigatory chamber, chaired by former Belgian Prime Minister Jean-Luc Dehaene, handed out the punishment after identifying that the clubs owed money to either other teams, their employees or had failed to pay taxes.
Atletico's fellow Spanish club Malaga, which is taking part in the Champions League for the first time this season, is another of the 23 clubs that has had the payment of prize withheld.
Sporting Lisbon, Hajduk Split, CSKA Sofia, Rubin Kazan and Fenerbahce are some of the others major clubs to have been sanctioned.
"I am still very worried about the current situation," Dehaene told the European Club Association's (ECA) general assembly. "The Financial Fair Play Regulations are known for more than two years, but I have the impression that some clubs still need to do their homework."
ECA Chairman Karl-Heinz Rummenigge added: "It seems that quite a few clubs have not understood the message. Time has come to take the new rules seriously. ECA will continue to support Financial Fair Play."
UEFA said the measure would remain in place until the clubs had paid the money they owed and have asked the 23 teams to provide an update on their finances by the end of September.
In a UEFA report published last year, it was estimated that about 50% of top European clubs were losing money and 20% were recording sizable deficits.
UEFA's Financial Fair Play (FFP) rules apply now but will come fully into force in 2014 and provide Europe's governing body with sweeping powers, including exclusion from the lucrative Champions League, if clubs fail to meet the regulations.
Under the new rules, owners can only contribute a maximum of $55.5 million for the 2013-14 and 2015 seasons together, and $37 million during the period covering 2015-16, 2016-17 and 2017-18.
Current rules state that should clubs incur losses in excess of $60 million over a three-year period, they will be hit with sanctions as well as exclusion from the Champions League and Europa League.
All clubs taking part in UEFA's competitions for the 2012/2013 season had to provide Europe's governing body with details of any "overdue payables" by the end of June.