Clubs should be wary of billionaire owners who spend enormous amounts on transfer fees and wages ahead of new rules that could ban clubs from European competitions for failing to balance the books, UEFA legal director Alasdair Bell said Friday.

''Clubs should not exist or continue to exist on the back of, shall I say, donations from wealthy benefactors who could be here one day and gone the next, leaving the clubs in a parlous position financially,'' Bell told a conference on law and football in Madrid.

Under financial fair play regulations, clubs face being barred from the Champions League and Europa League if they cannot break even on football-related business.

Those rules will have particular resonance for clubs like Manchester City, which lost 121 million pounds ($191 million) last year after Sheik Mansour Bin Zayed Al Nahyan spent $1 billion to transform the team, lavishing more on wages alone than the club's entire turnover.

Bell told The Associated Press that Manchester City would be among the clubs scrutinized when the regulations come into full effect for the 2013-14 season.

City recently announced the sale of naming rights for its City of Manchester Stadium, which became known as the Etihad Stadium in a 10-year sponsorship deal reportedly worth 100 million pounds ($159 million) with the Abu Dhabi-based airline.

Critics claimed that deal was just a creative way for Sheik Mansour to pump more money into the club in an attempt to skirt the UEFA rules.

''When the time comes, we'll have to decide whether that's a legitimate football income or whether it amounts to a capital injection by the owner,'' Bell said. ''It's not something we are looking at now, but when the financial fair play rules come into force, we'll have to have a discussion with them to have explanations about whether that's a genuine sponsorship deal.''

In Spain and Italy, season-opening matches have been lost because players refused to play due to contract disputes over unpaid wages. Six Spanish clubs started the season in bankruptcy protection.

Michel Platini, the former France star who heads European football's governing body, has acknowledged he is worried by the level of clubs' debt.

''There are a lot of red lights flashing,'' said Platini. ''I am afraid for the future of football. If football can't go ahead because players aren't being paid, that is a huge worry. We will not be forced to take a step back on this.''

Although the UEFA rules only apply to European competitions, Bell said he hoped they would be a ''model'' for national associations to institute in domestic leagues.

''One of the key principles is not to spend more than you earn or to live within your means. This is the cornerstone of the financial fair play concept,'' he said. ''The idea is that there should be a balance here that the football-related expenses should not be greater than the football-related revenues.''

Under the rules, unlimited spending is allowed on stadiums, youth training and other infrastructure that can help clubs become self-sustaining.

''Clubs should run their operations in a responsible and business-like fashion,'' Bell said. ''That means money is not just invested in paying a top player a higher salary.''