Football clubs who have agreed to join a European Super League “must answer to their fans” before going ahead with the “very damaging” change, the Prime Minister has said.

Boris Johnson posted his views on Twitter on Sunday evening, criticising the prospect of six English clubs possibly joining a breakaway continental league.

“Plans for a European Super League would be very damaging for football and we support football authorities in taking action,” said Mr Johnson.

“They would strike at the heart of the domestic game, and will concern fans across the country.

“The clubs involved must answer to their fans and the wider footballing community before taking any further steps.”

Manchester United, Liverpool, Arsenal, Chelsea, Tottenham and Manchester City later announced they have signed up to the plan, and will be joined by teams from Italy and Spain.

The move would see them create a competition for up to 20 clubs to rival the Champions League, but would not feature relegation or promotion.

Teams would play each other in midweek while still competing in their domestic leagues.

The mooted shake-up was widely criticised by political leaders including Culture Secretary Oliver Dowden.

Uefa, the football associations of England, Spain and Italy, plus the Premier League, LaLiga and Serie A have also spoken out against the move.

Mr Dowden described fans as the “heartbeat of our national sport” and said any major decisions about a European league “should have their backing”.

“With many fans, we are concerned that this plan could create a closed shop at the very top of our national game,” he said.

“Sustainability, integrity and fair competition are absolutely paramount and anything that undermines this is deeply troubling and damaging for football.”

Labour leader Sir Keir Starmer said the plan “cuts across all the things that make football great”.

“It diminishes competition. It pulls up the drawbridge. It is designed for and by a small elite. But worst of all, it ignores the fans,” he said.

European Commission vice president Margaritis Schinas said: “We must defend a values-driven European model of sport based on diversity and inclusion.

“There is no scope for reserving it for the few rich and powerful clubs who want to severe links with everything associations stand for.”

Fans’ groups, including those linked to Liverpool, Spurs and Chelsea, have also voiced their opposition to the clubs joining a super league.

Chelsea Supporters’ Trust said football fans worldwide have “experienced the ultimate betrayal”, adding: “This is a decision of greed to line the pockets of those at the top and it has been made with no consideration for the loyal supporters, our history, our future or the future of football in this country.”

Tottenham Hotspur Supporters’ Trust (THST) put out a statement calling for club owners Enic to “distance themselves from any rebel group”.

Arsenal fan Sir Keir said the clubs reportedly involved “should rethink immediately” and added that a non-domestic league “ignores” supporters.

“This proposal risks shutting the door on fans for good, reducing them to mere spectators and consumers,” he said on Twitter.

Fellow Gunners supporter and senior Tory MP Huw Merriman suggested teams who participate in the rebel competition should be expelled from the Premier League for this year.

“We could nip it in the bud straight away: either those six clubs disassociate themselves from this idea or expel them immediately from the Premier League competition for this year,” he told BBC Radio 4’s The Westminster Hour.

“They’ll soon backtrack. It’s grubby, it’s absolutely disgraceful. It has no regard for the culture of our game … It’s outrageous. And my own club Arsenal are part of it: I’m absolutely ashamed.”

Shadow sports minister Alison McGovern – a Liverpool supporter – demanded the Government “deliver on what they have promised: a proper, fan-led review of football governance”.

Sir Ed Davey, leader of the Liberal Democrats, said: “This is greed personified, ripping the heart out of the English game, leaving clubs up and down the country to suffer after an awful year.

“The consequences of these plans reach far and wide. The Government must step in to prevent a small number of greedy, rich owners destroying the game we all love.”