Losses incurred by top European clubs in 2010 leapt 36 percent from the year before to 1.6 billion euros ($2bn) due to lower revenues from transfers, UEFA said on Wednesday.
The deteriorating bottom line means that 56 percent of first-division clubs made losses in 2010, according to Andrea Traverso, head of licensing and financial fair play at UEFA, who presented the report at the football body's headquarters near Geneva.
"This trend needs to be reversed very quickly," said UEFA's general secretary, Gianni Infantino.
If new UEFA management requirements scheduled to come into effect from 2013-14 were imposed immediately, "13 clubs would not have passed the test," Infantino said.
Citing lower transfer revenues, he explained that while clubs' income increased between 2009 and 2010, it did not offset the higher expenses.
The UEFA report sets the total amount of transfer payments made during the year at 3.3bn euros.
Wages, however, remained stable at nearly 64 percent but continued to represent a significant share of clubs' spending, the report said.
UEFA also said that 52 percent of clubs registered in 2010 showed weaker balance sheets, indicating that many club owners did not cover their losses.
The governing body noted that less than 100 top-level clubs, or 75 percent of them, filled their stadiums in 2010, with more than half of those clubs in Germany, England and the Netherlands.