Europe's leading clubs have accused FIFA of attempting to "railroad" through plans for a biennial World Cup that they claim would have a "destructive" impact on the club game.
The European Club Association, which represents 234 clubs and is chaired by Paris Saint-Germain owner Nasser Al-Khelaifi, believes there has been a clear lack of consultation over proposed reforms to the International Match Calendar (IMC).
FIFA president Gianni Infantino is keen to introduce a World Cup every two years and that view has been supported in a series of interviews, including from the organisation's chief of Global Football Development and former Arsenal manager Arsene Wenger.
The ECA released a statement Friday morning describing this as a coordinated campaign and potentially in breach of a memorandum of understanding that governs the clubs' relationship with FIFA over any significant changes.
"ECA has been clear in its position that changes are needed to the IMC," read the statement. "A modernised and simpler IMC needs to be founded on fewer release windows; better player protection and health; and a balanced approach to club and international football.
"To that end, ECA has made clear -- publicly, privately and repeatedly -- its availability to engage with FIFA to agree what those changes should be.
"ECA has therefore followed with grave concern and alarm FIFA's launch of active PR campaigns and much pretence, apparently seeking to railroad through reforms to the IMC, particularly the introduction of a biennial World Cup.
"Aside from the notable lack of genuine [or indeed any] consultation, and as many stakeholders have pointed out in recent days, FIFA's proposals would lead to a direct and destructive impact on the club game, both domestically and internationally.
"In addition, the proposals would put players' health and wellbeing at risk. They would dilute the value and meaning of club and country competitions.
"They would diminish and conflict with women's and youth football -- being underrepresented areas of the game where ECA and others are committing significant time, talent and resources -- while also subordinating other sporting tournaments and interests at all levels worldwide."
UEFA has also criticised the proposal amid concerns over a loss of prestige and player welfare.
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Wenger was tasked by Infantino with performing a feasibility study voted for by 166 member associations of FIFA earlier in the year to examine ways to improve the calendar and a summit is set to be held on Sept. 30 to discuss changes that include confederation tournaments in odd years outside biennial World Cups and guaranteed rest periods of 25 days for players once tournaments are completed.
No changes can be implemented before 2024 at the earliest and the approval of the ECA will be required in order for players to be released for international competition.
Speaking to the BBC earlier this week, Wenger said: "After the proposal for the World Cup every two years sometimes [there is an] emotional response.
"I'm not surprised. Many people who were completely against it changed their mind after having seen my proposal.
"Some people have judged only based on every two years of World Cup and it was more emotional because 'we've all grown up in that cycle,' and I can understand that.
"But many responses who were negative came out because they had not completely seen the whole concept. This concept of course, every two years a World Cup, makes only sense if you see the whole proposal and if you regroup the qualifiers."