Manchester City and Paris Saint-Germain have both bristled at accusations of financial unfairness made by La Liga president Javier Tebas.
Both clubs have benefited from takeovers by wealthy Arab investors, with PSG sponsored by Qatar Sports Investment while City is owned by Abu Dhabi United Group.
City has spent £215m this transfer window, while PSG has splashed out on two of the most expensive signings ever with Neymar arriving for €222 and Kylian Mbappe set to cost €180m next year.
This has led Tebas to describe Spanish football as a swimming pool into which Neymar has "peed from the diving board", and has asked UEFA to investigate both PSG and City for breaching Financial Fair Play rules.
Referring to the oil-derived wealth of the club’s owners, Tebas insisted that "this is not the market price, it is the gas market price" and believes that "they are laughing at the system".
Tebas insists that the matter is not about PSG taking a star player from Barcelona, but that "they are affecting the economic structure of the league" and are "going to damage the industry".
"[UEFA] have created the financial fair play rules and we think these rules have been infringed," Tebas said.
"We believed UEFA need to carry out investigations. We believed the EU need to investigate, too. We are not hiding what we want to do.
"It's not that I don't like PSG. If Neymar had gone to Man United, it wouldn't have been as important to take this to the courts. They are not financial doping.
"What happens when this money coming into PSG and Man City comes into European football, there is an inflation of salaries and transfer fees. This is what we need to talk about."
While UEFA has launched an investigation into PSG, France’s Ligue de Football Professionnel (LFP) has leapt to the defence of the Parisians, saying they "condemn the insulting remarks made today by the president of La Liga, M. Javier Tebas" and "reaffirms its support for PSG in the face of a campaign of denigration".
Meanwhile, City Football Group, the owners of Manchester City, say they are "seeking appropriate legal counsel" and called Tebas' statements "ill-informed and in parts pure fiction".