The Alliance Party is opposing plans by the four main parties in Belfast City Council to introduce a new system for electing lord mayors.
The DUP, Sinn Fein, SDLP and UUP agreed at a council committee meeting that the lord mayor should be elected using the d'Hondt proportionality system.
The system is already used to allocate committee chairs and vice-chairs.
Councillor Maire Hendron said Alliance would oppose it because it was a deeply retrograde step.
"It would be unfair to employ a mechanism like d'Hondt as it would virtually prevent all independents from taking up these offices," she said.
"It also damages the chances of building consensus across all the parties, because there is nothing compelling them to reach agreements on genuinely sharing power if d'Hondt is in place.
"It sends out the message that we cannot take decisions like this in a mature and constructive manner."