Nwosu spoke in Owerri, the state capital.
He said the outcome of the election had shown that he was more popular than the APC governorship candidate, Hope Uzodinma.
He said he had put aside the injustice allegedly meted out to him by the leadership of the APC when he was a member of the ruling party.
He said the ruling All Progressives Congress made a mistake by denying him its governorship ticket.
The AA governorship candidate claimed that Uzodinma was an agent of the Peoples Democratic Party brought to APC to destabilise the ruling party.
He said, “The national leadership of the APC made a mistake by not giving the party’s governorship ticket to me. We warned them against giving the ticket to Hope Uzodinma, but the leadership of the party ignored our warnings.
“The outcome of the elections has justified us. We joined the AA two months to the election and I won the governorship election if not for the manipulations.
“We also won eight seats in the state House of Assembly. Action Alliance also won two seats in the House of Representatives.
“Now that they have realised their mistake, we are ready to form alliance with APC to reclaim our mandate.”
Nwosu said he filed a petition at the tribunal against the declaration of Emeka Ihedioha as governor-elect because the PDP candidate did not meet the constitutional requirements.
He described Iheodioha’s declaration by the Independent National Electoral Commission as an aberration.
“I have petitioned the tribunal and I am sure that the issues rose which bother on the constitution cannot be swept away.
“I am certain that I will reclaim my mandate in no distant time,” he said.