SABC station managers have been ordered in a secret memo to avoid broadcasting programmes involving "political discourse", citing the arms deal row, in the run-up to next year's election.
The memo said the decision had been taken against a background of discussion of corruption allegations against Deputy President Jacob Zuma.
The Broadcast Electronic Media and Allied Workers Union vowed to take the SABC to the Broadcasting Complaints Commission, accusing it of trying to gag presenters and prevent debate on Zuma.
Issued last week by Judi Nwokedi, the SABC's managing director of public broadcasts, the memo said all programmes, content and talk shows that involved "political discourse" should be "avoided absolutely".
Addressing station managers as "Dear Team", the memo reads: "As you are aware, we are heading into the campaign phase of election 2004. This means that various attempts for political jostling will be made by politicians across the country.
"One case in point is the current Zuma matter. I am therefore instructing all stations to categorically ensure that all programmes, content and talk shows that may vie in the direction of political discourse be avoided absolutely.
"The GCEO (group chief executive officer) has made a decision that editorially all this content will be driven by news under the leadership of Jimi Matthews (head of TV news) and Pippa Green (head of radio news)."
She said news and current affairs divisions would ensure coverage "on matters that are political".
A note at the bottom of the memo reads: "This instruction to you as station manager is in no way to be photocopied, stuck up on walls or on noticeboards."
It is understood that details of the memo leaked out when SAfm's acting station manager and programme manager Mike Roberts emailed its contents to his staff.
The SABC was swift to react, denying any claims that it was attempting to gag presenters by preventing them from discussing political issues.