The European Super League (ESL) is a "disgraceful, self-serving" plan and a "spit in the face of football lovers", says Uefa president Aleksander Ceferin.
He also said players who play for teams involved in the closed league would be "banned from the World Cup and Euros".
Arsenal, Chelsea, Liverpool, Manchester City, Manchester United and Tottenham are among 12 clubs agreed to sign the proposed ESL.
UK culture secretary Oliver Dowden announced a fan-led review of football.
Dowden said the review had been brought forward and would offer a "root and branch" review of the sport, covering finance, governance and regulation.
He said while football's authorities are equipped to handle the proposed ESL breakaway, the UK government would provide "full backing".
"Be in no doubt, if they can't act, we will," added Dowden. "We will put everything on the table to prevent this from happening. We are examining every option. Put simply, we will be reviewing everything the government does to support these clubs."
Labour welcomed Dowden's statement but said it was "short on detail and the urgency this situation merits".
A YouGov poll of 1,730 football fans found 79% opposed the idea of a European Super League, with 68% of those polled stating they are strongly opposed to the move.
Ceferin, who has been Uefa president since 2016, has overseen an agreement on a new-look 36-team Champions League but made clear his disdain for the ESL project.
"We are all united against this nonsense of a project," he said.
"I cannot stress more strongly how everyone is united against these disgraceful, self-serving proposals, fuelled by greed above all else.
"[It is a] cynical plan, completely against what football should be. We cannot and will not allow that to change.
"Players who will play in the teams that might play in the closed league will be banned from the World Cup and Euros. We urge everyone to stand tall with us as we do everything in our power to ensure this never ends up in fruition.
"This idea is a spit in the face of all football lovers. We will not allow them to take it away from us."
The ESL will be a "new midweek competition" with teams continuing to "compete in their respective national leagues".
After it was announced on Sunday, Fifa expressed its "disapproval" of the proposed competition and called on "all parties involved in heated discussions to engage in calm, constructive and balanced dialogue for the good of the game".
World football's governing body previously said it would not recognise such a competition and any players involved could be denied the chance to play at a World Cup.
The 14 Premier League clubs not signed up to the ESL will meet on Tuesday to assess the proposals and consider a response.
On Monday, Ceferin reiterated clubs and players involved with the ESL could be banned "as soon as possible" from all Uefa competitions.