In a lengthy statement which marks an escalation of tension between the game's two most powerful organisations, UEFA also claimed FIFA is yet to respond to a request for a meeting to discuss the proposals.
FIFA is conducting a feasibility study into holding the men's and women's World Cups every two years from 2028 as part of a radical reorganisation of the football calendar.
The plans are the brainchild of Arsene Wenger, now FIFA's chief of global football development, who has insisted they will reduce the strain on players and lead to more meaningful top-level matches.
UEFA and all of Europe's top divisions, including the Premier League, are fiercely opposed to the plans.
Outlining "just some of the serious concerns" with the proposals, UEFA said scrapping the four-year World Cup cycle would see the tournament lose "mystique" and negatively impact players, smaller national teams and the women's game.
UEFA's statement read: "There are real dangers associated with this plan:
– the dilution of the value of the no.1 world football event, whose quadrennial occurrence gives it a mystique that generations of fans have grown up with;
– the erosion of sporting opportunities for the weaker national teams by replacing regular matches with final tournaments;
– the risk to sustainability for players, forced to engage in summer high intensity competitions every year instead of longer recuperation breaks in alternate years;
– the risk for the future of women’s tournaments, deprived of exclusive slots and overshadowed by the proximity of top men’s events."
Earlier this month, Wenger briefed reporters on the benefits of the plan and UEFA also criticised FIFA's approach to promoting their reforms.
UEFA called for "genuine consultation" and "an open discussion" between FIFA, the international confederations and national competitions.
Their statement added: "[These concerns] cannot be dispelled simply with unsubstantiated promotional slogans on the supposed benefits of a thicker calendar for final tournaments."
UEFA also said FIFA's feasibility study must take into account a number of factors, including the impact of biennial World Cups on: existing club and national competitions, players' mental and physical health; supporters; the football eco-system; the women's game; youth football; and the global sports system.