The European Professional Football League (EPFL) has angrily rejected UEFA's reforms of the Champions League and Europa League which were announced last month.
UEFA gave four guaranteed Champions League group-stage places to the top four leagues -- the Bundesliga, La Liga, the Premier League and Serie A -- and redistributed the prize money to better reward historic success in European football.
But the EPFL, the umbrella organisation that represents European football's professional leagues, has accused UEFA of breaching the terms of the deal that governs club competitions in Europe and says reforms were made "without the support and consensus'' from the domestic leagues.
"This decision will have a detrimental impact on domestic competitions and will lead to an exponential growth in the financial and sporting gap between the biggest clubs in Europe and all the others,'' a statement from the EPFL board of directors said.
"As a result of the decision taken by UEFA, the EPFL believes that UEFA has breached the Memorandum of Understanding between the two organisations.
"In the event that the EPFL were to terminate the MoU as a result of such breach, this would give all European leagues total freedom to schedule their matches as they see fit, including on the same days and at the same kick-off times as UEFA club competitions.''
Responding to the EPFL statement, UEFA's acting general secretary Theodore Theodoridis said: "The evolution of UEFA's club competitions is the result of a wide-ranging consultative process involving all European football's stakeholders, including the European Professional Leagues, and taking into account a wide range of expertise and perspectives.
"The amendments made will continue to ensure qualification based on sporting merit, and the right of all associations and their clubs to compete in Europe's elite club competitions.
"We are happy that the concepts of solidarity, fair competition, fair distribution and good governance remain at the core of European football."
The EPFL has been backed by a number of smaller Bundesliga clubs, who fear that the reforms will cement the current status quo in Germany.
Earlier this week, German football magazine kicker reported that Europe's top clubs are set to earn over €100 million in the 2018-2019 season following changes to the distribution of Champions League revenue distribution.
According to kicker, that could mean top Champions League clubs earn €60m more per season, while smaller clubs could see an increase of only €6m.
"The top six spots in Bundesliga are usually taken by the same clubs. The redistribution of the Champions League revenue should only cement that development," TSG Hoffenheim finance executive Frank Briel said.
FC Cologne executive Alexander Wehrle added: "It's incredibly important for the national leagues that the sporting competition continues to exist. There are always two teams on a pitch, and there should be a realistic chance for both to win. Everyone profits from that."
Bayern Munich CEO Karl-Heinz Rummenigge, who also acts as the chairman of the European Club Association [ECA], had described the changes as "an evolution, not a revolution," and added that all clubs will "profit" from it.
Rummenigge's counterpart at Dortmund, Hans-Joachim Watzke, also told kicker that the "tendency towards the big clubs" could not be stopped in a globalised world.
Neil Doncaster has added Scottish opposition to Champions League changes after the group that represents European leagues hit out at the reforms.
SPFL chief executive Doncaster said: "Notwithstanding the welcome retention of a route to the Champions League for the SPFL's Ladbrokes Premiership winners, we absolutely share the EPFL's disappointment about the regressive and protectionist direction of travel for the world's most prestigious club competition.
"There needs to be a far stronger balance between sporting merit and commercial pressures, otherwise we risk an inexorable slide towards an NFL-style closed-shop system. We know that many of our counterparts in other countries share our concerns about the nature of the decision-making process and the lack of consultation with European leagues.
"UEFA has a duty to act on behalf of the entire game, not just a few, select clubs and leagues and it must take that duty far more seriously if it is not to risk presiding over a harmful fragmentation of the game.
"As we said recently, we will continue to be robust and forthright when required in fighting to protect the best interests of Scottish football on this issue, with today a strong demonstration that the majority of other European leagues share our view."
The EPFL threat to rip up this agreement comes a week before UEFA gathers in Athens to elect a new president. European football's governing body has been in limbo since current incumbent Michel Platini was banned from all football activities for corruption last year.
The statement from EPFL's board calls on the new president, who will be either Slovenia's Aleksander Ceferin or Dutchman Michael van Praag, to reconsider the reforms and says the leagues are ready to meet him for urgent talks.
Ceferin, the frontrunner, is perceived to be more attuned to the concerns of smaller nations and has a reputation as a consensus-builder, whereas van Praag is thought to be closer to Europe's more powerful clubs, although the EPFL gathering is at Ajax, where he served as chairman between 1989 and 2003.
ESPN FC's Germany correspondent Stephan Uersfeld contributed to this report.