European Professional Football Leagues (EPFL) is a body that represents the Premier League, Bundesliga and La Liga.
It criticised Platini's proposals to restrict the number of clubs that can qualify from each country to three and allow domestic winners an automatic route to the group stages.
"It is important that we look after the clubs' interests and these are just two things which are concerning us," EPFL director general Emanuel Macedo de Madeiros said.
"We believe what is being proposed is not in the best interests of the leagues.
"UEFA is the ultimate entity that is responsible for the Champions League, but we are concerned at the impact and the amendments being discussed."
England, Spain and Italy annually provide four Champions League entrants, meaning more money from television and advertising revenues into those leagues.
Platini would prefer a greater number of clubs from less rich nations to take part.
"We understand that it is vital for European football to have strong domestic leagues," De Madeiros continued.
"Anything which could affect negatively the league's competitions would be detrimental to the whole of European football."
Any changes to the format of the continent's showpiece club competition would come into effect for the 2009-2010 season.