A Premier League supporters' group has accused Uefa of attempting to return to the "discredited idea of a European Super League" with its plans to revamp the Champions League.
A 12-team European Super League was announced last year.
However, all but three clubs - Juventus, Real Madrid and Barcelona - pulled out after widespread protests.
Around the same time, Uefa unveiled plans for a revamped 36-team Champions League, starting in 2024.
The expanded competition will increase the number group stage matches from six to 10 and reserve two qualification spots to allow clubs to participate based on historic European performance instead of domestic achievement.
Uefa's executive committee will make a final decision on the plans on 10 May, but the Football Supporters' Association's Premier League Network said the proposed 36-team tournament would "entrench the richest clubs, damage the English football pyramid and rip off fans".
"We are united in opposition to proposals to reform the Champions League that are a back door attempt at a return to the discredited idea of a European Super League," read the FSA Premier League Network statement.
"Last year, it was our supporter groups that united to force the collapse of the European Super League. At the time, Uefa told us that fans were the heart of the game and promised fans' views would be centre stage in deciding what came next.
"So it is with great dismay that we now face the prospect of changes to the Champions League that will mean many more group games being played and entry for some clubs being based on a historical five-year 'Uefa club co-efficient'.
"These proposals will only widen the gap between rich clubs and the rest, at the same time wrecking domestic league calendars, with the expectation that fans sacrifice yet more time and money attending meaningless group games."
Uefa proposals 'irresponsible and out of touch'
The new format will see 36 clubs qualifying for an expanded first phase, where all clubs play against 10 opponents of varying strengths.
This will result in a league table, with the top eight qualifying for the knockout phase and the next 16 going into a play-off to determine the remaining eight slots.
Under its latest proposal, teams could only qualify via the co-efficient if they finished immediately outside the regular Champions League spots, to avoid them leapfrogging rivals who finished in a higher position.
However, the FSA Premier League Network's statement said such plans were "irresponsible and out of touch", stating it could double the number of home matches in the group stages in a competition that favours the continent's richest cubs.
"Premier League fans do not want 10 group games involving a small cartel of rich clubs further distorting competitive balance," the statement added.
"We want strong, competitive domestic leagues, an equal opportunity for all to qualify for Uefa competitions based on sporting merit, along with a fairer distribution of the game's wealth from the revenues those competitions earn.
"Last year, we engaged in constructive discussions with Uefa president (Aleksander) Ceferin who made a commitment that fans would be listened to in this process. Our collective voice is unified and our position clear.
"We call on Uefa to demonstrate that it acts in the interests of the wider football community and its supporters, not just the interests of the few rich investors and state-owned clubs that, less than a year ago, tried to destroy the European football family."