Calls to nationalise the personal wealth of black economic empowerment (BEE) tycoons Tokyo Sexwale and Patrice Motsepe were based on jealousy, African National Congress (ANC) secretary-general Gwede Mantashe said on Tuesday.

"It's talking to the resentment we have among ourselves as black people. If anybody progresses we feel very jealous and we resent their success," Mantashe told a media briefing at Luthuli House in Johannesburg.

The National Union of Metalworkers (Numsa) has called for nationalisation of the wealth of South Africa's richest man, Motsepe, and that of ANC struggle hero, Tokyo Sexwale. Both have benefited from government's BEE policies.

"We should deal with that [the jealousy] and not beat about the bush as if it's a nationalisation debate. It is not a nationalisation debate that is raised by Numsa," Mantashe said.

He described it as a "strange phenomenon", since in the recently published top 100 richest South Africans, there were only 20 blacks. Having the State take the wealth of these 20 would hamper transformation.

Mantashe condemned the public attack on the ANC's treasurer general Mathews Phosa by the Gauteng Young Communist League.

"We must emphasise that personal attacks and vilifications are the surest way of derailing and killing any debate."

The league had criticised Phosa for saying that mines in the country would not placed under the State's control.

Mantashe said such personal attacks weakened the alliance between the ANC, the Congress of South African Trade Unions (Cosatu) and the South African Communist Party.

Attacks on individuals by the structures in the alliance would be discussed in bilateral meetings next week.

Minister in the Presidency Trevor Manuel was also personally lambasted by Cosatu after he released a Green Paper on national planning.

"We think it's a destructive way of dealing with each other, it is not helping our cause, it's actually weakening the alliance.

"We are talking of a principle here that it doesn't matter who you are talking to, once you begin to be personally attacking a person or vilifying a person... actually you are not inviting that person for a discussion or a debate, you are killing it," Mantashe said.

This also applied to people outside the ruling alliance.