Uefa angered by G14 'smokescreen'
Uefa is convinced the G14 group continues to harbour hopes of breaking away from the Champions League.
The G14 group represents 18 of the world's most powerful clubs.
Uefa chief executive Lars-Christer Olsson said: "They are creating a smokescreen to hide their ambitions for an alternative competition."
And he warned the G14's £740m claim for compensation in the Charleroi case over players injured on international duty needed to be taken "very seriously".
Belgian club Charleroi, backed by G14, are taking world governing body Fifa to court, claiming compensation over a player injured in an international match.
Moroccan Abdelmajid Oulmers was out for eight months after playing against Burkina Faso in November 2004.
G14 wants the regulations surrounding the compulsory release of players for international matches changed and clubs to be compensated if players are injured playing for their countries.
Olsson added: "I tend to judge people on what they do and not so much on what they say.
"So if you have a claim from the G14 clubs, written down on paper, in a court case in Charleroi, demanding £600m for compensation for players released for international duty then I take that very seriously.
"Now we hear they are asking for another £140m from Fifa for payment for players in the World Cup.
"G14 have tried to distance themselves from that figure but they have not withdrawn that claim from the court.
"This is a challenge that everyone in football should take seriously."
G14 'happy' as key case referred
The G14 group of leading football clubs say they are "very happy" a landmark court case has been referred to the European Court of Justice.
A Belgian court referred the case against Fifa, brought by Belgian club Charleroi with the backing of G14, to Europe's highest court in Luxembourg.
The case concerns Charleroi player Abdelmajid Oulmers who was injured while playing for Morocco in 2004.
G14 clubs want compensation when their players are injured on internationals.
Oulmers was sidelined for eight months after suffering his injury in Morocco's game against Burkina Faso in November 2004.
Charleroi say the loss of the player hindered their chances of success in the Belgian league and cup.
Fifa maintained there is no link between the injury of Oulmers and Charleroi's fifth-placed finish in the league.
G14 general manager Thomas Kurth said: "Fifa's argument was that it's rules were not in any eay subject to EU law.
"But we asked for a ruling at the European Court of Justice on these rules, which we've always said are unfair to every club, not just G14 members."
The G14 has already joined Olympique Lyon in a similar action over defender Eric Abidal, who broke his foot during a France friendly.
Clubs pay the wages of players, which can exceed £100,000 a week for the top performers.
Jean-Phillipe Lebeau, president of the commercial tribunal in Charleroi, said: "The European Court of Justice is the only court that can sufficiently decide this case, taking everything into account."
The last major case in football to be referred to the European Union's highest court also started in Belgium.
The 'Bosman' ruling, after a case brought by player Jean-Marc Bosman, gave players the choice to move freely between clubs when out of contract, thereby increasing player power.
