Jean-Luc Dehaene, chairman of Uefa's Club Financial Control Panel, says clubs must respect Uefa's financial rules and also work within the spirit of the law.
Under the financial fair play rules, which come into force this summer but do not take full effect until 2013, teams will not be able to spend more than the income they generate from the football side of their business - which includes gate receipts, TV deals and sponsorship.
Any side unable to match the criteria could be barred from playing in European competition - the Champions League and the Europa League.
Manchester City's sponsorship deal with Etihad Airways - a 10-year deal reportedly worth £400m - will be analysed by Uefa's financial fair play (FFP) boss.
City declined to reply to Dehaene's interview, although the club has previously said speculation over the figures was "not accurate".