UUP Cllr Jeff Dudgeon was speaking after City Hall passed a Sinn Fein proposal preventing councillors from using “offensive expressions in reference to any person or section of society”.
Branding the move “ludicrous”, Cllr Dudgeon said the plan may be open to legal challenge as it could conflict with Article 10 of the European Convention on Human Rights, which guarantees freedom of expression.
He told BBC’s Talkback programme yesterday: “One man’s offensiveness is another man’s virtue.
“At present, the lord mayor can rule on anyone who is using offensive expressions against other members in the chamber.
“But henceforth, she will have to rule on whether any section of society might be offended be a members’ remarks.
“It is ludicrous and goes way beyond the normal rules of debate.”
PUP Cllr John Kyle said the motion was putting forward a solution to a problem we don’t have”.
He added: “The existing standing order is quite adequate to control offensive language.
“We need to be very careful when bringing in rules which restrict freedom of speech, unless that speech is bringing harm to some people.”
During Wednesday’s debate at City Hall, loyalist councillor Jolene Bunting also expressed her opposition to the motion, claiming it would restrict her ability to criticise Islam.
“It is very clear this motion is trying to silence some members of this council,” the independent unionist told members.
“What worries me is that in future we are not going to be able to speak out about problematic members of society in Belfast.
“It (the proposal) infringes our human rights and freedom of expression.”
Cllr Bunting, who was recently banned by Facebook for 30 days after posting messages in support of a member of far-right group Britain First, added: “We must be able to speak our minds and stand up for our constituents.
“Do we have to wait until people are dying on our streets until people actually speak about Islam, before we speak about the Koran, and what it says in it?”
Responding to Cllr Bunting’s comments, SF member Jim McVeigh told the chamber: “We just got a glimpse of the nasty side of this city in some of those remarks.
“These comments are a very good example of why we should make these changes (in the proposal).”
Alliance Cllr Emmet McDonough Brown, who backed the motion, said “damaging remarks” have been made in the council chamber about sections of society here.
He added: “We feel there are minority groups in this city who are being targeted at a political level and it is important that we uphold their rights in their absence.”