Speculative proposals for a "European Premier League" comprised of the continent's top clubs and reportedly backed by FIFA were criticised on Tuesday by La Liga and supporter groups.
A Sky report on Tuesday claimed that negotiations were nearing conclusion on an 18-team league with end of season playoffs including the likes of Real Madrid, Barcelona, Liverpool, Manchester United and Bayern Munich.
According to the report, the project would be funded by $6 billion (5.1 billion euros) of financing from major banks secured on the proceeds from future TV broadcast deals. Each of the participating clubs could receive "hundreds of millions of pounds to participate".
A European Super League has long been touted as the way for major clubs to further increase their revenue streams, but it would come at the cost of the Champions League and national leagues.
Although the report claims the proposals would see clubs continue to compete in national leagues with European matches in midweek, that would put extra strain on an already highly congested calendar.
"These 'underground' projects only look good when drafted at a bar at five o'clock in the morning," said La Liga president Javier Tebas.
"The authors of that idea -- if they really exist, because there is nobody actually defending it -- not only show a total ignorance of the organisation and customs of European and world football, but also a serious ignorance of the audiovisual rights markets.
"A project of this type will mean serious economic damage to the organisers themselves and to those entities that finance it."
The latest leak over proposed reform of the game comes just over a week since Liverpool and Manchester United's "Project Big Picture" plans to restructure English football were rejected by Premier League clubs.
Those plans aimed to cut the Premier League to 18 teams and scrap the League Cup to make more room in the calendar for European matches.
"If you're a club owner or football financier who thinks a global health crisis is the perfect opportunity to rip up and reshape football to suit billionaires...you have no idea how much fans detest your concept," said the Football Supporters Association in England. "It will not go how you think."
A shake-up of European football is expected when broadcast contracts for the Champions League expire in 2024.
UEFA's initial proposals of an extended group stage and system of promotion and relegation for Champions League qualification were met with derision from clubs and leagues whose chances to compete in Europe's premier club competition would be squeezed.
The 2020/21 Champions League group stage gets underway on Tuesday in the traditional format of eight four-team groups with the top two in each section progressing to the last 16.