The government has said it will do "whatever it takes" to prevent a breakaway European Super League involving six leading English clubs.
Boris Johnson said ministers would be working to make sure the league did not go ahead in the way being proposed.
The Duke of Cambridge also said he shared fans' concerns about "the damage it risks causing to the game we love".
But the president of Real Madrid told a Spanish TV show: "We are doing this to save football at this critical moment."
Florentino Perez, president of Real Madrid, said the decision to create the new league was in part taken because "young people are no longer interested" in the game.
Speaking for the first time since the league was announced, Mr Perez said: "Audiences are decreasing and rights are decreasing and something had to be done. We are all ruined. Television has to change so we can adapt."
The 12 founding members of the league, which includes Real Madrid plus three yet to join - would be permanent and never face relegation.
Six English clubs - Arsenal, Chelsea, Liverpool, Manchester City, Manchester United and Tottenham - have signed up to the league
They would join Spanish sides Atletico Madrid, Real Madrid and Barcelona and Italian clubs AC Milan, Juventus and Inter Milan.
The competition would have 20 teams and another five sides would have to qualify each year for the competition.
Matches would take place midweek and rival the existing Champions League.
But the president of European football's governing body Uefa, Aleksander Ceferin, warned players who play for teams in the ESL would be "banned from the World Cup and the Euros".
As opposition to the plans gathered momentum, Prince William, President of the Football Association, said in a tweet: "Now, more than ever, we must protect the entire football community - from the top level to the grassroots - and the values of competition and fairness at its core."
And broadcaster Sky Sports said: "We have not been involved in any discussions with the proposed breakaway European Super League."
"We are completely focused on supporting our long term football partners in the UK and in Europe, already providing fans with the best live action from the best football competitions in the world," the company added.
In a statement to MPs in the House of Commons, Culture Secretary Oliver Dowden criticised the so-called "big six" English clubs for going "against the very spirit of the game".
He added club owners "should remember that they are only temporary custodians of these clubs and that they forget fans at their peril".
Mr Dowden said he had spoken to Uefa and the Football Association, who both oppose the move by the 12 clubs, adding that, "if they can't act, we will".
"We will put everything on the table to prevent this from happening," he told MPs.
"We are examining every option from governance reform to competition law and mechanisms that allow football to take place.
"We will be reviewing everything Government does to support these clubs to play. We will do whatever it takes to protect our national game."
A fan-led review, due to take place after the pandemic, has been brought forward because of the ESL announcement, Mr Dowden said.
It will be led by former sports minister Tracey Crouch and consider how fans can have an even greater say in the oversight of the game.
The review will also look at the finances of the men's and women's game, its governance and whether an independent football regulator should be set up.
Earlier, Prime Minister Boris Johnson said the government was "going to look at everything that we can do with the football authorities to make sure that this (plan) doesn't go ahead in the way that it's currently being proposed".
Downing Street said ministers were looking at a "range of options", including a German-style system of fan ownership of clubs and clawing back coronavirus support loans.
But Labour urged ministers to do more, with shadow culture secretary Jo Stevens saying it was "time for the government to get off the subs bench and show some leadership on the pitch because we need reform of football".
She added: "It's not as if there's been a blockage here in Parliament preventing the government from taking action to sort the problems out."
Fans and pundits have expressed revulsion at what they claim would be an unfair competition that would lock many teams out of top European football.
Match of the Day host and former England footballer Gary Lineker said it was "a time of great concern", adding that if the ESL went ahead as planned, it would have "massive ramifications" on the domestic game.
"It will wreck the pyramid system (of leagues, promotion and relegation) that has been so important to local football clubs, communities and teams, and it takes out the competition."
Around 68% of football fans strongly oppose the creation of the ESL, while only 14% support it, according to a YouGov survey of 1,730 fans.
Some 700 football supporters gathered outside Leeds United's Elland Road ground ahead of the club's Premier League game against Liverpool to protest against the proposed new league.
A Liverpool shirt was burned and a plane flew over the stadium displaying an anti-Super League message.
Inside the stadium Leeds players wore T-shirts saying 'Earn it' next to the Champions League logo and 'Football is for the fans'. A banner behind one goal had the same message.
Launching their plan, the 12 founding members of the ESL said the pandemic had "accelerated the instability in the existing European football economic model".
They said there was a "need to provide higher-quality matches and additional financial resources for the overall football pyramid".
BBC's Sports Editor Dan Roan said leading figures were insisting the Super League would generate much more money, not just for the clubs involved, but for the rest of the "football family".
He added they seemed "very confident" they were on a strong legal footing when it came to blocking any punishments threatened by bodies such as Uefa.
Earlier, Manchester United's shares rose within minutes of the opening bell on the New York Stock Exchange, where they are traded.
Fifteen minutes after the trading day began, they were up around 8.5%.
Meanwhile, Juventus's share price jumped by more than 14% on Monday morning.
But Liverpool manager Jurgen Klopp has said he remained opposed to the idea of the league - despite his club agreeing to join it.
"I like the competitive aspect of football. I like that West Ham might play in the Champions League," he said, adding that he and his players did not know about the move before it happened.