La Liga president Javier Tebas compared the reports of a new European Premier League to a project that was drawn up in a bar at 5am in the morning.
Reports in England on Tuesday suggested Liverpool and Manchester United were leading a group of clubs that would break away from the UEFA Champions League to feature in a tournament drawn up by FIFA.
Barcelona, Real Madrid and Atletico Madrid would be the Spanish teams theoretically involved in such a league, which would supposedly feature 16-18 teams.
The competition would no doubt have an effect on domestic leagues, too, where there would be strong opposition to any new European league.
"The authors of that idea - if they really exist, because there is nobody actually defending it - not only show a total ignorance of the organization and customs of European and world football, but also a serious ignorance of the audiovisual rights markets," Tebas said.
"A project of this type will mean serious economic damage to the organizers themselves and to those entities that finance it, if they exist, because they're never official. These 'underground' projects only look good when drafted at a bar at 5 in the morning."