President Kgalema Motlanthe has said ANC head of elections Fikile Mbalula should explain why he wrote an open letter about former president Thabo Mbeki, the Sunday Times reported.

"I have been trying to muster enough courage to read it so that I can talk to him about it," Motlanthe was quoted as telling the Sunday Times.

"I did chat to the secretary-general (Gwede Mantashe) about it to find out what could have triggered this, and he was not clear," said Motlanthe.

Earlier this week, Mbalula wrote an open letter to Mbeki accusing him of being "conniving" and of betraying the legacy of former president Nelson Mandela.

In his letter, Mbalula said Mbeki decided to "spawn" the ANC breakaway party, the Congress of the People, after being defeated as ANC leader by Zuma at the Polokwane conference in December 2007.

At a briefing on Tuesday, Mbalula said Mbeki was "politically responsible" for the conspiracy against Zuma as he was the head of government at the time.

In an interview with the Sunday Times, Motlanthe said he had "difficulties" with any member of the ANC who "decides to define any member of the ANC (as) outside the ranks of the (party) without due processes.

"The ANC constitution is very clear on the obligations and rights of each member."

Motlanthe said as a "bona fide" ANC member, Mbeki deserved to be treated fairly and with respect.

"This is the least he deserves."

Motlanthe told the Sunday Times that the practice of ANC members using open letters to address each other "needs to be nipped in the bud."

"I just think it is unbecoming... I do not think it is a healthy way of either engaging or conversing as members...because you can foster divisions in the organisation by doing that."

Motlanthe told the Sunday Times he would speak to Mbalula to find out why "he thinks his letter enhances the ANC's image and chances in the elections."

The Sunday Times reported that Mbalula said on Saturday that he stood by the views he expressed in the letter.

"I remain firm in my views expressed in the letter and I therefore neither require permission of the ANC deputy president in advancing such views as a member of the ANC nor expect him to agree with those views," Mbalula was quoted as saying.

"It is rather disingenuous of comrade Motlanthe to suggest my actions are un-ANC when Thabo Mbeki's actions had all the hallmarks of undermining the unity and integrity of the ANC, yet he never saw it fit to call him to order," Mbalula told the newspaper.