Councillors could be asked to overturn a decision to honour a Coleraine-born "unsung hero" of the American Revolution.
Objections have been lodged against moves to celebrate Hercules Mulligan in the Causeway Coast and Glens area.
It comes after records showed he owned a slave after helping to set up an anti-slavery society.
Mulligan's family emigrated to America in 1746, when he was six. He went on to spy on the British during the American War of Independence and in 1785 was a founder member of the New York Manumission Society, which campaigned to abolish slavery.
According to official US records, however, he still owned a slave five years after establishing the organisation, with one even living with his family.
Alliance councillor Yvonne Boyle, who proposed that Mulligan be recognised through local heritage trails, said she knew he had owned a slave before she put forward the motion.
Other councillors told this newspaper they were not in possession of this fact ahead of a successful vote on the plan.
Sinn Fein's Dermot Nicholl, the chair of the council's leisure and development committee, said he was alarmed that councillors had not been presented with a full account of Mulligan's past.
In light of this, he added, he would seek to have the decision overturned if it came before the council again.
"His history as a slave owner was not alluded to when this proposal was brought to the committee, so the vote we took was based solely on the information presented to us by councillor Boyle," Mr Nicholl explained.
"Had we known that this man was a slave owner, we most definitely would not have supported this proposal.
"I have already contacted the director of the leisure and development department, Richard Baker, expressing concern.
"If this comes to full council, we will retake our decision in relation to this proposal."
Ulster Unionist councillor Joan Baird said she "would have thought long and hard" about supporting the plan had she known more about Mulligan.
"What we were told was that he was an honourable person. I would have expected the Alliance Party to have done its homework and given us (a full) assessment of the situation," she added.
"I expect this will come before the council again. I will make my decision on the information."
Stephen McCracken, from the Limavady Area Ancestry history group, criticised the decision to honour Mulligan.
"When I saw in the Press that the council was going to honour him, I was horrified," he said.
"It is wholly inappropriate that a slave owner should be given any kind of recognition."
Lilian Seenoi-Barr, chair of the North West Migrants Forum, also hit out at the move, saying her group intended to write to the council, asking for the decision to be overturned. "Calling Hercules Mulligan a hero when he was still a slave owner five years after he helped set up the New York Manumission Society is glorifying slavery and that is disgraceful," she said.
Alliance councillor Boyle, however, defended her decision.
"Whilst it is common knowledge he owned a slave - and that is a reprehensible practice - it is important to look at it through the context of the time," she said.
"Many of America's founding fathers were slave owners, and Cato, Mulligan's slave, helped him in his work as a spy. Many believe that he was given his freedom after the war.
"It is vital, however, that this is not ignored. Any future heritage trail must include his slave-owning and abolitionist history when mentioning Hercules Mulligan."