Paris Saint-Germain president Nasser Al-Khelaifi said Barcelona's asset sales in the summer to fund signings were "not fair" and suggested UEFA would investigate their legality.
Barca sold stakes in their domestic television rights and Barca Studios, an in-house production company, for over €700 million to allow them to spend more than €150m on the arrivals of Robert Lewandowski, Raphinha and Jules Kounde. Five other players arrived as free agents.
"Is this fair? No, it's not fair. ... Is it legal? I'm not sure," Al-Khelaifi said in an interview with Politico published on Wednesday.
"If they allow them, others will do the same. UEFA of course have their own [financial] regulations. For sure they're going to look at everything."
Barca were forced to sell off the assets to comply with LaLiga's strict regulations and register their new signings with the Spanish league.
By selling off 25% of their LaLiga media rights and a 49% stake in Barca Studios -- which will now branch out into web3 and blockchain projects -- they increased their league-imposed annual spending limit from minus-€144m to over €600m.
While LaLiga have cleared the funding, Al-Khelaifi's comments hint that UEFA will delve further into the legality of the business.
Al-Khelaifi's latest comments are an escalation of remarks he made on Friday, when he indirectly criticised Barca during a speech to European club bosses.