UEFA president Aleksander Ceferin has said that any clubs involved in the Super League will be banned from taking part in the Champions League and Europa League.
Ceferin, speaking at the Financial Times' Business of Football Summit in London, was asked about new plans for the Super League which are set to be presented by Juventus chief Andrea Agnelli.
"I am tired of talking about this nonsense," Ceferin said.
"First they try to launch during a pandemic, now we hear that they are trying to launch in the middle of a war. Do I have to speak more about these people? They obviously live in a parallel world.
"While we are saving players together with other stakeholders, while we are working to help in a terrible situation they work on a project like that.
"Honestly speaking, they can pay whoever they want to write that this is a nice project, that they are full of solidarity and give some charity to small clubs. This is a complete nonsense and everybody except them knows it.
"One of them even called me after and apologised. Now they go again.
"To them fans are customers, for us fans are fans. It is interesting that they are criticising UEFA and ECA, one of them [Agnelli] was chairman of the ECA. Fans aren't important to them as fans launched a petition, they don't care about that.
"Let me just say that they can play their own competition, nobody forbids them that. But if they play their own competition they cannot play our competition."
Agnelli is ready to present a new vision for the Super League at the summit in London, after seeing previous plans rebuffed last April.
Agnelli was a key figure last year when Juventus and 11 other clubs announced plans for a breakaway competition that would have usurped the Champions League, causing uproar across Europe.
Unlike before, Agnelli will reveal that the plans would be for an 'open' competition with no fixed spots and instead of replacing the Champions League would operate like the Nations League does at international level.
The Super League was originally unveiled last April with Juventus, Real Madrid and Barcelona - three clubs who have been pursuing legal action against European football's governing body ever since the initial project imploded - leading the charge along with AC Milan, Inter, Atletico Madrid and six Premier League clubs.
Manchester United, Manchester City, Liverpool, Chelsea, Arsenal and Tottenham Hotspur were all part of the original scheme, but soon backed away following mass protests from their own fans which forced them all to make public apologies.
La Liga chief Javier Tebas joined in the attack against Juventus, Real Madrid and Barcelona at the summit in the English capital, adding: “They lie more than Putin!
“I feel humiliated by the idea of relaunching the Super League. These three teams are insulting us. "He [Agnelli] will have to explain it, if he doesn't explain it, he will be lying.
"They are insisting that introducing this will not affect national leagues. We must be idiots, we must be dumb. But we all say it hurts the national leagues."