The government will take "whatever action necessary", including legislative options, to stop plans for a European Super League, No 10 says.
Following the PM's meeting with the FA and Premier League officials, and fans' representatives, Downing Street said: "No action is off the table."
The 12 founding members of the league faced a fierce backlash after unveiling proposals for a breakaway tournament.
One of these, Real Madrid, insisted they were doing it to "save football".
Club president Florentino Perez said the decision to create the new league was in part taken because "young people are no longer interested" in the game.
He told a Spanish TV show: "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 president of European football's governing body Uefa, Aleksander Ceferin, has warned players who play for teams in the ESL that they would be "banned from the World Cup and the Euros".
But in a letter to Uefa and Fifa, seen by the BBC, lawyers for the ESL say they have filed injunctions to prevent player and club bans, saying they consider such actions to be "unlawful".
An insider at the ESL said they had prepared themselves for a huge backlash, and thought they were on firm legal ground with respect to competition law.
"I think in the cold light of day, they are looking at this and the reality is dawning that this is happening and it's perfectly legal," they told the BBC.
A Spanish court has temporarily blocked any attempt by Uefa or Fifa to ban clubs or players from leagues or competitions, in an interim ruling to prevent any bans before the legal basis of this can be tested.
ESL insiders said "this looks aggressive but we had to take defensive action in the face of threats from Uefa and Fifa - our hope is we can ultimately resolve this in negotiations".
The 14 Premier League clubs not participating in the new venture "unanimously and vigorously" rejected the plans for the competition and are "considering all actions available to prevent it from progressing".
A statement released on Tuesday said they "call on those clubs involved in the proposed competition to cease their involvement immediately".
One of these, Everton, released a statement criticising the "preposterous arrogance" of the clubs involved.
Downing Street said the prime minister told his meeting with FA and Premier League officials that the government "will not stand by while a small handful of owners create a closed shop".
Boris Johnson reiterated his "unwavering support for the football authorities and confirmed they have the government's full backing to take whatever action necessary to put a stop to these plans", a statement said.
He also made it clear "that no action is off the table and the government is exploring every possibility, including legislative options, to ensure these proposals are stopped".
The prime minister's official spokesman said among the measures under consideration were preventing players of the clubs involved getting work visas and the withdrawal of police funding for match days.
Chief executive of the Football Supporters' Association, Kevin Miles, told BBC Radio 4's World at One programme: "The mood music from the government was they would do what was required to make sure that the measures to exclude those [ESL] clubs from competitions would not fall foul of competition law, and that they would amend the law if necessary."
UK watchdog the Competition and Markets Authority said it would be "carefully considering any competition aspects of these proposals".
The proposed league has united MPs from every party against it. Suggestions from MPs on action the government could take include governance reform, changes to competition law, changes to taxpayer support for clubs and border controls on arrivals into the UK.
The Arsenal Supporters' Trust said it was "delighted" to hear the government's promise of action, adding that the PM vowed the football governance review led by Conservative MP and former sports minister Tracey Crouch would be "swift".
There have been protests by fans across the country against the proposed league, including outside Chelsea's Stamford Bridge ground on Tuesday.
How would the European Super League work?
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 in an attempt to have more matches between the big-name clubs and rival the existing Champions League.
The plans revealed on Sunday that the 12 founding football clubs would be permanent members and never face relegation.
Critics say the new league could supplant the existing Champions League and disrupt the current football "pyramid" that sees teams rise or fall on merit.
Read more here.
Former England captain Alan Shearer told BBC Breakfast the six English clubs should be expelled from the Premier League, which they have said they aim to remain in while also playing in the European Super League.
"It's not right what they are doing, it's not competitive, it's a closed shop - you can't have a competition where no one else is allowed in," he said.
"You can hear, feel and see the anger from almost everyone in football."
Chairman of the Commons' Digital, Culture, Media and Sport Committee Julian Knight, said restricting work visas for footballers who play in the proposed ESL could be one way the government could pull levers to stop the league going ahead.
Speaking to the BBC, he said other options were a windfall tax on clubs and long-term reform giving fans much greater power on football club boards.
Labour leader Sir Keir Starmer said he thought the "threat of legislation will have an effect" but the government needed to act quickly.
Lib Dem leader Sir Ed Davey called for "real action" from the government, suggesting a new law requiring owners to ballot season ticket holders before committing clubs to newly formed competitions.
And on Monday, the Duke of Cambridge, who is president of the Football Association, said he shared fans' concerns about "the damage it risks causing to the game we love".
Gianni Infantino, president of the world football's governing body Fifa, said he "strongly disapproves" of the plans.
"If some elect to go their own way, they must live with the consequences of their choice. They are responsible for their choice completely. This means you are either in or you are out. You cannot be half in and half out."
Sky Sports confirmed it had "not been involved in any discussions" about the breakaway league.
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