UEFA president Michel Platini described Real Madrid's world record bid for Manchester United's Cristiano Ronaldo as "excessive" at a time when the world is in the midst of a financial crisis.
"It is very puzzling at a time when football faces some of its worst ever financial challenges," Platini said in a statement to Reuters.
"These transfers are a serious challenge to the idea of fairplay and the concept of financial balance in our competitions," he added.
The head of European football's governing body was referring to Madrid's 80 million-pound bid for Portugal winger Ronaldo and their recent signing of Brazil midfielder Kaka for about 68 million euros (57.8 million pounds).
The chairman of the French League, Frederic Thiriez, was also critical of the fees, saying: "Those amounts are neither understandable nor justifiable. Those excesses will lead the sport to the wall. I ask for a European financial regulator."
French clubs often complain they are not on a level playing field with teams in other countries due to the French League's strict financial rules, which forbid huge amounts of debt.
In November, EU sports ministers mulled the possibility of a pan-European financial regulator for sport but decided instead to press football's world ruling body FIFA and UEFA to introduce stricter financial rules for clubs and leagues.
UEFA officials said they hope to put forward new plans this year to tighten financial regulation such as cutting excessive club debt and imposing stricter rules on player transfers.
UEFA is also considering limiting the amount of revenue a club can spend on transfers and wages to about 45-55 percent of revenue from ticket sales, television rights and sponsorship.
There would be no limit on money invested by club owners but this would have to be used for projects such as infrastructure, including stadium development, and improving youth academies.
UEFA is also looking into the possibility of limiting the number of professional player contracts that can be issued in each country across Europe to reduce the size of squads.
Platini's special advisor William Gaillard told Reuters earlier this year that reducing the number of professional contracts had "become more favourable" than the UEFA president's proposal to directly cap wages and transfer fees.
(Reporting by Darren Ennis; Additional reporting by Etienne Ballerini in Nice; Editing by Ed Osmond and Ken Ferris)