BBC Sport reports that Man City and PSG are being accused of financial doping by La Liga president Javier Tebas.
Tebas says the clubs had spent money from outside football and action should be taken to stop it.
Tebas said PSG were “laughing at the system” after their world record £200m purchase of Neymar from Barcelona.
He added: “We’ve caught them peeing in the swimming pool. Neymar peed from the diving board. We can’t accept this.”
“It is not just about PSG but also Manchester City. I need more money from TV, otherwise, Manchester City with its oil will take all these players.”
European football’s governing body Uefa is investigating if PSG have broken Financial Fair Play rules but are not looking into Manchester City, despite La Liga calling for it do so.
City’s summer spend of £215m was the biggest by any club in any transfer window and included deals for England full-back Kyle Walker (£45m), Portugal midfielder Bernardo Silva (£43m), Brazilian goalkeeper Ederson Moraes (£35m) and France defender Benjamin Mendy (£52m).
PSG more than doubled the world record transfer fee when they signed Neymar last month, before adding Kylian Mbappe on loan from Monaco, a deal that is expected to be made permanent for £165.7m in 2018.