A video circulating on social media shows a group, The Druids, apparently performing songs inciting hatred and glorifying terrorism.
Councillor Nuala McAllister said: “This type of inflammatory language only serves to keep Northern Ireland stuck in the past, entrenched firmly in the tribal lines that define our troubled history.
“It is extremely disappointing that a group of performers – grown men – would be so reckless as to increase tensions by fuelling sectarian division at a public event, an event that had crowds of young people in attendance.
“I will be raising this incident with Belfast City Council. All publicly funded events should make full efforts to ensure they remain free from the divisive hatred seen on display on Sunday night. Belfast City Council aims to promote a diverse cultural mix of events, open and inclusive to everyone. Incidents like those seen on Sunday night will only serve to create further divisions.
“The Ardoyne fleadh should learn from other examples of cultural events. The success of the All-Ireland fleadh, held in Derry in 2013, is a fine example of an event which respectfully celebrated Irish cultural heritage, whilst remaining open and inclusive to the whole community.
“Alliance is the only Party dedicated to working for everyone – to build a new Northern Ireland free from intimidation, sectarianism and fear and a place where our unique diversity is cherished and celebrated. The silent majority must stand with us as we seek an end to division and segregation and work towards building the genuine shared future we all deserve.”