Motlanthe revealed that former president Thabo Mbeki would also join the party's efforts to canvass support in the local government elections next month.
Motlanthe, accompanied by ANC Gauteng chairman Paul Mashatile, paid a surprise visit to DA leader Mmusi Maimane's home in Dobsonville to try to persuade the family to ditch their son's party and vote for the ANC.
They spoke to Maimane's father, Simon, who was once a member of the ANC.
"We had to converse with him. He received us very well. He is an old resident here," said Motlanthe, who went door-to-door in Dobsonville to ask residents to vote for the ANC.
Simon Maimane declined to speak to Motlanthe and Mashatile in front of the media, so the ANC heavyweights met him in private.
"We didn't want to cause any strife in the family," Motlanthe later joked.
Mabine Seabe, spokesman for the DA leader, described Motlanthe's visit to the Maimane home as "an act of desperation".
He said: "The people of Dobsonville and the Maimane household are for change and the DA in 2016.
"It's an act of desperation to send a former president to campaign at the Maimane home."
Seabe said the DA would be in Dobsonville today to convey its message of change.
Motlanthe said he and Mashatile had delivered the ANC's message to Maimane snr, but the way he decided to vote would be his secret.
Since his retirement from active politics in 2014, Motlanthe has appeared briefly at ANC campaign events.
But he said he remained an active ANC member and would help the party when needed.
"It's all hands on board now. All of us need to come out and assist the candidates," said Motlanthe.
He said Mbeki would soon join him on the streets.
"You will see him in the streets very soon ... You will definitely see him," Motlanthe said.
Mashatile said all ANC leaders would have to come and assist the party.
"If all of us come out then victory is certain," he said.
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