Mbalula, the ANC's head of organising, told a media briefing in Cape Town that the party had "long reached" the million mark.
"In fact we've got a problem of overpopulation of our members," he said.
However, there were problems with the ANC's computer system which used to "disaggregate" new memberships. This was being sorted out.
"By March this year we are going to invite you to the biggest-ever extravaganza of the launch of Imvuselelo in Johannesburg," he said.
Imvuselelo is a campaign initiated some years ago to build branches and recruit members.
"Going towards 2012 is going to be another story," Mbalula added.
"In fact I think we'll be above one million, chasing five million up there in terms of ANC memberships."
Fellow NEC member Mathole Motshekga said the ANC's computer system had not been able to accommodate all the people who wanted to join.
"There are indeed people outside the system who should have been inside the system a long time ago," he said.