LaLiga team Atletico Madrid criticised on Thursday a "dangerous precedent" set by the Spanish national sports council (CSD) to allow Barcelona midfielder Dani Olmo to play on a temporary basis after his licence expired.
Olmo and forward Pau Victor were unregistered by LaLiga after Barcelona failed to get their short-term licences extended before the end of 2024.
The Catalans sought and were granted a precautionary measure by the CSD on Wednesday, while their case against LaLiga and the Spanish football federation's decision is analysed, which would allow Olmo and Victor to play until there is a final ruling.
"Atletico Madrid wish to express their deep concern about the situation in Spanish football following the resolution adopted this Wednesday by the (CSD)," said the club in a statement.
"We believe that this decision puts the current system in jeopardy, questioning the rules of the game.
"This government intervention creates a very dangerous precedent, as it opens the door to breaking the rules and making the same serious mistakes of the past."
Financially-struggling Barcelona were not in a position to register Olmo and Victor under LaLiga's strict financial fair play rules, until they agreed a deal to sell some VIP seats to Middle Eastern investors in late December, with the paperwork not ready until after the deadline.
Without the missing players Barcelona beat Athletic Bilbao to reach Sunday's Spanish Super Cup final in Saudi Arabia.
Las Palmas were also upset with the decision by the CSD.
"We believe that this decision poses a serious threat to the integrity of the competition and sets a worrying precedent that could destabilise the foundations of professional football in our country," said Las Palmas in a statement.
LaLiga president Javier Tebas railed against the decision to let Olmo and Victor play, calling the situation a "tragicomedy" in a post on social media.
Tebas expressed his surprise at the CSD measure and highlighted that it contradicted previous decisions made by the council and some courts.