Earlier this month, UEFA president Aleksander Ceferin said the global football showpiece tournament will lose "legitimacy" if it's held every two years.
UEFA says it still has "serious concerns" about FIFA's controversial proposal to hold the World Cup every two years instead of four.
Football's world governing body has invited the sport's domestic bodies to an online summit on September 30 to discuss a potential biennial World Cup.
But UEFA is still concerned about a possible "dilution" of the event caused by staging it more regularly, as well as effects on player welfare and the women's game.
It also hit out at the way FIFA has promoted its plans, largely through media interviews and press conferences.
"UEFA is disappointed with the methodology adopted, which has so far led to radical reform projects being communicated and openly promoted before having been given, together with other stakeholders, the chance to participate in any consultation meeting," read the UEFA statement.
It added that the "real dangers" associated with holding the World Cup every two years also included "the erosion of sporting opportunities for the weaker national teams.”
UEFA statement on proposals for a biennial World Cup ⬇️— UEFA (@UEFA) September 22, 2021
Earlier this month, UEFA president Aleksander Ceferin said football's showpiece tournament would lose "legitimacy" if not held only once every four years.
The World Cup has been held every four years, besides cancellations due to World War II, since the inaugural edition in 1930.
The push to increase the number of World Cups has been led by former Arsenal manager Arsene Wenger, now director of development at FIFA.
"On 14 September, UEFA and its 55 member associations asked FIFA to organise a special meeting with them to be able to voice their concerns on the impact of such plans," UEFA added on Wednesday.
"UEFA and its 55 member associations have to-date not yet received a reply from FIFA on this request."
The body also listed a series of "issues" it expected to be studied in FIFA's feasibility study into holding the World Cup biennially.
FIFA president Gianni Infantino has promised a decision on the matter by the end of 2021.
Earlier this year, UEFA announced a revamped and expanded version of its own international Nations League tournament.