This comes after Young Communist League national secretary Buti Manamela said Mbeki and former health minister Manto Tshabalala-Msimang had denied many HIV-positive people access to anti-retroviral drugs while they were in government.
Manamela made a call for the two of them to be charged with genocide.
"We must never surrender our leaders," said Malema at a gala dinner of the Pan African Youth Union at Emperor’s Palace in Boksburg on Monday evening.
"Thabo Mbeki might have made mistakes but we can never charge him."
"We must not charge one of our own. If we allow that, the same thing would happen to [Zimbabwean President Robert] Mugabe, and the same would happen to [President Jacob] Zuma, and the next thing you know they will come for you," Malema said.
Malema said it was important for the ANCYL to support Zimbabwe’s Zanu-PF.
"But we do not support only one individual," he said. Speaking to the congregation of youth organisations of Southern Africa, Malema said the youth of Zimbabwe must stabilise the country.
He said while Mugabe did many good things, he must not use them to cling to his position.
"Those who have led for a long time must allow new leaders to come in," said Malema about African leaders’ tendencies to cling to power.
"We have refused that in South Africa."
Malema said South Africa’s struggle was not over.
"As long as we do not have economic power, our vote means nothing," he said.
He said South Africa’s economic power was still in the hands of white males, who still controlled production in the country.
"We must refuse to be slaves of those who want to control Africa with remote controls from their golf estates," he said.
Advocating nationalisation Malema said the ANCYL did not plan to "grab land as they are doing next door".
He said while he supported the idea that land must be owned by Africans, "we have to respect the rights of the current owners".
He said the ANCYL supported the idea of willing buyers, willing sellers, but that the owners must not test the ANCYL’s patience.
"You cannot steal my car and fit it with mags and everything and when I find it in Soweto you tell me I have to pay for it," he said. "You must be arrested."