The expulsion is contained in a press statement signed by Omoyele Sowore, chairman of the party on Monday.
Ezenwa was earlier in the day announced as the new national chairman after the party said it had suspended Sowore for alleged corruption.
Sowore said: “It has come to the notice of the office of the Chairman of the African Action Congress that a group of suspended members, induced by financial reasons and anti-progressive politics, gathered in Abuja today, 13th May, 2019, and purportedly held a NEC meeting.
“These members, led by Leonard Nzenwa, former national secretary, who was suspended for financial impropriety and anti-party activities, have demonstrated by their actions that they have never been, and have never shared, the core beliefs that those of us in the African Action Congress hold.
“Leonard Nzenwa is hereby expelled from the party, and the misguided individuals who participated in the Abuja meeting are suspended from the party until investigations reveal the extent of their involvement.”.