"His position is clear. Leaders must respect the right of branches to elect leaders," said Motlanthe's spokesperson Thabo Masebe.
"Nothing must be done to take away that right."
When leaders aligned themselves with particular factions, or canvassed support, it led to divisions within the ruling party.
"Once they [leaders] get involved in any discussions, it means they have already decided they want leadership positions."
Masebe was speaking after the Sunday Times reported that Motlanthe had rejected overtures from a Zuma-aligned lobby group which wanted to cut a deal for the party's leadership.
Many in the ruling party are said to favour Motlanthe as the party's next leader over President Jacob Zuma.
Earlier this week, Winnie Madikizela-Mandela attacked Zuma in an MTV interview scheduled for September, the paper reported.
It was difficult to promote a single sexual partner to young people when the president had multiple partners, she reportedly said.
"People have to redefine an acceptable culture that is going to define you as an African and, at the same time, retain your dignity as an African," the Sunday Times quoted her as saying.
She also hinted she was opposed to the Protection of State Information Bill.
"I'm sure you would know what I would think about that [Bill]," she reportedly said, noting that ANC MP Ben Turok had abstained from voting on the Bill and was facing disciplinary action as a result.
League endorses Motlanthe
Meanwhile, ANCYL deputy president Ronald Lamola on Saturday said it was a tradition in the ANC for deputy presidents to later be elected as president of the organisation.
"One day comrade Kgalema Motlanthe will become president of the ANC," Lamola said at the youth league's Nelson Mandela memorial lecture in Hillbrow, Johannesburg.
"It is written in the history books of the ANC," he said. – Sapa