Fifa must postpone its expanded Club World Cup or face the prospect of legal action, the international ­players’ union has warned, in a fierce broadside against the game’s global governing body.

Fifpro and the World Leagues organisation have written jointly to Fifa’s president, Gianni Infantino, asking him to reschedule the 32-team tournament, which is set to take place in the US next June and July. The new Club World Cup, ­alongside its old iteration now rebranded as the ­Intercontinental Cup, should be paused until a full agreement on the shape of the ­international match calendar can be agreed, the letter says.

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“Fifa’s recent strategic approach of developing its own competitions – such as the World Cup, the Club World Cup or the Intercontinental Cup – is adversely disrupting the football industry, jeopardizing national leagues and affecting the health and wellbeing of players,” the letter says.

“Over a significant period, Fifa has ignored repeated attempts by leagues and unions to engage on this issue. Leagues and players cannot simply be expected to ‘adapt’ to Fifa’s decisions, which are driven by Fifa’s business strategy. We have reached the point where this situation must immediately be addressed both from a procedural and substantive perspective.”

The letter, sent to Infantino last week, calls on Fifa to announce the rescheduling of the Club World Cup and Intercontinental Cup at its global congress in Bangkok next week. If not, the letter says, “we shall be compelled to advise our members on the options available to them … to ­proactively safeguard their interests. These options include legal action against Fifa, on which we have now commissioned external expert advice.”

The tone of the letter is excoriating and echoes recent comments made by the chief executive of the Premier League, Richard Masters, who said the match calendar was “at a tipping point” and described an absence of consultation from Fifa over proposed changes.

Fifa is yet to comment publicly on the letter but has made the case that the Club World Cup conforms to rules around rest periods for players, with three-day gaps between fixtures and the capability for players to take a minimum of three weeks’ break before returning to their clubs for the league season. Fifa also makes the case that participation in its combined club ­competitions would make up 2.1% of the average schedule for a club who play in an 18-team domestic league and have qualified for Europe.

The new Club World Cup is the latest proposed expansion of the men’s football calendar. Next season Uefa’s club ­competitions are set to grow, with the Champions League expanding from 32 clubs to 36 and the number of group fixtures from six to eight. International competitions are also growing, with the Fifa World Cup ­contested by 48 nations over five weeks in the ­summer of 2026.

At the same time the ability of governing bodies to assert their control over the ­calendar has been weakened by the ruling of the European court of justice, in the case of the abortive European Super League, where the court found that governing ­bodies had to provide proper ­consultation with leagues, clubs and other stakeholders and that any decisions on new tournaments had to be “transparent, objective, non-discriminatory and proportionate”.