Ohanaeze said that there are legal processes used to determine if a group is a terrorist organisation or not.
The defense headquarters (DHQ) had on Friday, September 15, declared IPOB a "militant terrorist" organisation following the group's clash with soldiers in Abia State last week.
The DHQ said members of the IPOB had at different times attacked soldiers with sticks and stones in the state.
Hours after the Army declaration, south-east governors also banned IPOB in the region.
But the Ohanaeze in a statement opposed the DHQ, saying the IPOB is not a terrorist group.
It said that there are legal processes used to determine if a group is a terrorist organisation or not.
The Ohanaeze also asked the army to stop its 'invasive' operation in the south-east immediately.
"That the decision of the Nigeria army to commence Operation Python Dance in the south-east at this point in time is regrettable and called for immediate termination of the exercise. The military option is never the solution to problem of nation building. We refer for instance to goings on in Spain, Scotland and other parts of the world to reaffirm that only through dialogue can the national question be resolved. Consequently we condemned all acts of violence in pursuance to freedom of expression," the nine-point statement signed by John Nwodo, said.
"That Imeobi resolved that IPOB is not a terrorist organisation. There are processes under extant national and international laws, especially the Terrorism Prevention Act 2011, as Amended in 2015 to determine whether a group is or not a terrorist organisation."
Ohanaeze regretted the loss of lives during the recent military intervention, describing it as "unfortunate and deplorable."
"It is the sole responsibility of the police in every democracy to maintain law and order and protection of lives and property of its citizens.
"A united Nigeria under a restructured federal system of government that guarantees justice, equity and fairness is the best system for this country.
"Accordingly, Ohanaeze is mandated to organise a special summit soonest of Igbo nation in support of the restructuring agenda", it said.
The Igbo socio-cultural organisation added that the continued policy of marginalisation of the south-east is the primary cause of the renewed agitation by the IPOB group.