The ANC has slapped National Planning Minister Trevor Manuel on the wrist for acting like a free agent in publishing a scathing letter against government spokesman Jimmy Manyi.

"The NWC [national working committee] further appealed to all ANC members to stop and refrain from behaving as if they are free agents who speak as individuals, reflecting comments that are not informed by policy," ANC secretary general Gwede Mantashe said in a statement read to reporters in Johannesburg.

Asked if he was referring to Manuel, Mantashe replied: "We refer to Trevor Manuel or anybody who is a member of the ANC... [because] to act as free agents as they wish, then you might as well not have an organisation so it's not only about Comrade Trevor, it's about everybody."

Last week, Manuel wrote an open letter to Manyi in which he called him a "worst-order racist" following comments by Manyi last year that there was an "over-supply" of coloured people in the Western Cape.

Manyi's comments made headlines after the Solidarity trade union last week posted the Kyknet interview in which he made them on YouTube.

He later said he had been speaking in his capacity as president of the Black Management Forum.

Opposition parties called on Manyi to step down. The SA Municipal Workers' Union (Samwu) called for his head.

Mantashe chose to defend Manyi.

"Anything that it catches, smells. That's what it looks like in the case of Jimmy Manyi. Up to now, nobody has raised the question of incompetence on the part of Jimmy.... In my own view, I think it's a question of hatred for change," said Mantashe.