Top associations including UEFA, the English Football Association and the Premier League have said they're "united in [their] efforts" to prevent the "cynical project".
French President Emmanuel Macron said Sunday his government would support attempts to stifle the creation of a controversial European football "super league".
Any clubs intending to push ahead as part of a European Superleague, warned that this would / could then see them barred from all domestic competitions, any other officially sanctioned European /World competition, plus players of any club taking part in a European Superleague finding themselves nearly certainly barred from playing for their countries in World Cups and European Championships.
20 European clubs consisting of 15 permanent members plan to kick the Super League off from 2022-23, but Europe's biggest leagues and UEFA are against the idea and have released joint statements condemning it.
It continued, "As previously announced by FIFA and the six Federations, the clubs concerned will be banned from playing in any other competition at domestic, European or world level, and their players could be denied the opportunity to represent their national teams".
Uefa said it thanked "those clubs in other countries, especially the French and German clubs, who have refused to sign up" to the breakaway league.
They said they will "remain united" in trying to stop the breakaway, using both judicial and sporting measures if required.
"They should deduct six points off all six teams that have signed up to it".
The Premier League is proud to run a competitive and compelling football competition that has made it the most widely watched league in the world. Deduct points off them all.
He added: "In the midst of a pandemic, an economic crisis, football clubs at National League level going bust almost, furloughing players, clubs on the edge in League One and Two - and these lot are having Zoom calls about breaking away and basically creating more greed?" To do it during a season?
The Football Supporters' Association said it is "totally opposed" to the plans, which it said were "motivated by nothing but cynical greed". Obviously, we've not heard anything from Federation Internationale de Football Association yet, but it doesn't sound good. "It's just pure greed".
The other major European leagues also condemning the proposals, as well as UEFA.
The letter, signed by 17 fans' groups from 14 teams whose clubs are in the ECA, including Ajax, Real Madrid, Bayern Munich and Borussia Dortmund, said it was a "blatant power grab" and would "wreck domestic calendars".