Juventus were the only club to agree with the reform, while Inter Milan, AC Milan, Roma and Fiorentina declined to vote.
The Premier League, Bundesliga, Ligue 1 have already opposed a potential reform.
“Any semi-closed model will endanger the value of national competitions,” the Serie A clubs said in the resolution.
“We also express our concerns about the economic and competitive impact on Serie A of this UEFA reform.
“We truly hope that UEFA will take our observations into consideration and will work together with the European Leagues to implement a different model that will preserve the sustainability of both national championships and European competitions.”
The ECA, whose chairman Andrea Agnelli is Juventus president, says it wants to help clubs outside the biggest five leagues by giving them more regular European matches