Plans for a breakaway European Super League are a "spit in the face of all football lovers", the president of UEFA has said.
Aleksandr Ceferin said players at the 12 clubs setting up their own midweek league, including Arsenal, Chelsea, Liverpool, Manchester City, Manchester United and Tottenham, will be banned from international competitions, such as the World Cup and European Championships.
The other ‘founding clubs’ who have signed up are Italy’s AC Milan, Inter Milan and Juventus, and Atletico Madrid, Barcelona and Real Madrid of Spain, with three others anticipated to join ahead of the inaugural season.
There has been widespread criticism of the new plans from fans, former players, managers and governing bodies, who have warned it will "devalue" existing club leagues and competitions and have a devastating impact on grassroots football.
Speaking after an emergency meeting of European football’s governing body, Ceferin launched a scathing attack on the proposals.
The proposed new competition is a rival to UEFA’s established Champions League format which currently dominates European football.
Ceferin said: "UEFA and the footballing world stand united against the disgraceful self-serving proposal we have seen in the last 24 hours from a select few clubs in Europe that are fuelled purely by greed.
"The players who will play in the teams that might be playing in the closed league will be banned from playing the World Cup, and so they will not be able to represent the national teams at any matches.
"In my opinion, this idea is a spit in the face of all football lovers, and our society as well. So we will not allow them to take it away from us."
He added: "It is not just football, societies and governments across Europe are united, we are all united against this nonsense of a project.
"We have English FA, Spanish and Italian federations, FIFA, all 55 member associations unanimous in opposition against these cynical plans.
"Our sport has become greatest based on sporting merit and we cannot allow that to change, we will not ever."
A joint statement including UEFA and the English, Italian and Spanish leagues on Sunday said it would consider "all measures, both judicial and sporting" to prevent the competition going ahead.
Twelve of the leading clubs in Europe last night announced their intention to form the new breakaway league. Teams would play each other in midweek while still competing in their domestic leagues.
In a letter to UEFA and world football’s governing body FIFA, seen by the PA news agency, the Super League said it had begun legal action aimed at fending off threats to block the new competition.
The league wrote: "We are concerned that FIFA and UEFA may respond to this invitation letter by seeking to take punitive measures to exclude any participating club or player from their respective competitions.
"We hope that is not your response to this letter and that, like us, your organisations will recognise the immediate benefits of the competition established by SLCo (Super League Company)."
It added: "SLCo has filed a motion before the relevant courts in order to ensure the seamless establishment and operation of the competition in accordance with applicable laws."
Qatari-owned Paris St Germain and European champions Bayern Munich, which is majority-owned by the fans, have not signed up to the plans, meaning that France and Germany are not represented in the Super League as things stand.
The breakaway clubs will be guaranteed annual places in the new competition – in contrast to the current Champions League, which requires teams to qualify via their domestic leagues.
Some analysts think the announcement may prove a ploy by the big clubs, some of them highly indebted, to extract more money from existing competitions after a year in which the COVID-19 pandemic has hammered their revenues.
"Whether it’s Super League or not, the signal is that the big clubs want to ‘renegotiate’ with UEFA the proceeds, so it’s definitely something that stirs the waters…," said Angelo Meda, head of equities at Banor SIM in Milan.
"I doubt that they have moved like this and will give in, something will be granted."
Boris Johnson says the government will do everything it can to make sure the new European Super League "doesn’t go ahead in the way that it’s currently being proposed", calling the plans "very damaging for football".
The prime minister said he would work with football authorities opposed to the move, adding: "I don’t think that it’s good news for fans, I don’t think it’s good news for football in this country."
He said: "These clubs are not just great global brands – of course they’re great global brands – they’re also clubs that have originated historically from their towns, from their cities, from their local communities, they should have a link with those fans, and with the fan base in their community."
Mr Johnson said the six Premier League clubs involved "must answer to their fans" before deciding to launch the breakaway competition.
Culture, Media and Sport Secretary Oliver Dowden said he had met with the Premier League, the FA and the president of UEFA, and have given them the government’s full backing in trying to block the proposal.
"Be in no doubt, if they can’t act, we will. We will put everything on the table to prevent this from happening," Mr Dowden told parliament.
"We are examining every option from governance reform to competition law and mechanisms that allow football to take place."
Chelsea head coach Thomas Tuchel has insisted he trusts his club to make the right decisions on the Super League, revealing he only found out about the Blues’s entry on Sunday.
The German believes it is too soon to make hard and fast judgements but conceded he wants to manage in the world’s top competitions.
"I’ve known since yesterday," said Tuchel. "I’m here to be in the hardest competitions, that’s why I came here, that’s what I love, to play the toughest competitions in Europe.
The announcement of the new league came a day before UEFA was meeting over plans for an expanded and restructured Champions League tournament.
The Super League has also been criticised by Labour Party leader Sir Keir Starmer, who said the plans had ignored the fans – and urged a rethink.
The competition will see 20 participating clubs – 15 founding clubs and a further five teams able to qualify annually based on their achievements during the previous season.
The Super League will begin in August with clubs participating in two groups of 10, playing home and away fixtures, some during the week, with the top three in each group qualifying for the quarter-finals.
Teams finishing fourth and fifth will compete in a two-legged play-off for the remaining quarter-final spots before a knockout format is used to reach the final at the end of May, which will be staged as a single fixture at a neutral venue.
In exchange for their commitment, founding clubs will receive an amount of €3.5bn (£3bn) to "support their infrastructure investment plans and to offset the impact of the COVID pandemic", the league’s statement said.