European fan groups have accused the continent's top soccer clubs of "crisis profiteering" and called on them to drop plans for changes to the Champions League.

UEFA are expected to vote on Wednesday on plans to expand the Champions League to 36 clubs, increasing the number of games in a new format.

The group, Football Supporters Europe (FSE), has written an open letter to Juventus president Andrea Agnelli, who is chairman of the European Club Association (ECA), saying the plans present a "serious threat to the entire game".

"You will only make the gap between the rich and the rest bigger, wreck domestic calendars, and expect fans to sacrifice yet more time and money," the fans wrote.

The letter is signed by supporters' groups of clubs on the ECA's board including Manchester United, Arsenal, Bayern Munich and Real Madrid.

The ECA has backed the plans which have also been criticised by the European Leagues body, which represents domestic competitions.

The supporters' groups said the plans would benefit "a handful of already wealthy clubs, investment firms and sovereign funds, none of which have the legitimacy to decide how football should be run. Even most ECA members stand to lose out from the proposed reforms".

The supporters were critical of the changes coming during a pandemic.

"Such a blatant power grab would be indefensible at the best of times, but at the height of a global pandemic it is nothing more than crisis profiteering, not to mention a stark contrast to the solidarity displayed by fans.

"Over the past year, we have supported our clubs unconditionally, buying season tickets with no hope of attending games, and paying for TV subscriptions to watch repetitive ties held in empty, soulless stadiums, all while you were working behind the scenes to find new ways to bleed us dry," they added.

The fans' groups said they did not want to see more European games and wanted to see a fairer distribution of resources.

"We therefore demand that you drop your reckless plans. We also call on football's governing bodies to stop making concessions to elite clubs and intervene to protect the future of the game," the letter concluded.

The ECA did not immediately respond to a request for comment.