Premier League clubs have opposed proposed changes to the Champions League format from the 2024-25 season, one of which would see four groups of eight teams resulting in more matches.
According to reports, the European Club Association, led by Juventus chairman Andrea Agnelli, plans to meet Uefa in May to discuss the revamp.
English clubs have highlighted “significant concerns” about the plans.
They added they would work to “protect” the Premier League.
Their fear is that the increase of group-stage games – from six to 14 – would affect the schedule of the domestic league.
A statement on behalf of the 20 Premier League clubs, said: “All clubs unanimously agreed it is inappropriate for European football bodies to create plans that would alter the structures, calendar and competitiveness of the domestic game and will work together to protect the Premier League.
“In England, football plays an important role in our culture and everyday life.
“Millions of fans attend matches across the country, with allegiances and local rivalries often passed down through generations.
“We have a fantastic combination of competitive football and committed fans that we will vigorously defend.
“The structures of domestic football are determined by leagues and their respective national associations.
“We will now work with the Football Association and other leagues to ensure that European football bodies understand the importance of this, and their obligation to maintain the health and sustainability of domestic league football.”