"It has been reported to us by several of our members that they have been instructed to not report on any activities of the expelled ANC Youth League leader, Mr Julius Malema," the Broadcasting, Electronic, Media and Allied Workers Union (Bemawu) said on Thursday.
"The instruction went as far as to say that even if he is assassinated, or he dies in any other manner, it should not be reported until top management has instructed otherwise."
SABC spokesperson Kaizer Kganyago said the allegations were not true.
"It is untrue that the SABC news department has issued any instructions banning Julius Malema. What news management has appealed for, is for more responsible and in depth reporting on the issues," Kganyago said.
SABC acting head of news Jimi Matthews said in statement that he had asked the news team to provide more context in their stories.
"I am very disappointed with the turn of events. Instead of debate, certain members of my staff ran off to other media houses claiming that I had banned Malema from the airwaves," he said.
"Nothing can be further from the truth. I asked for responsible journalism and intellectual engagement".
'Attack on freedom of the press'
Bemawu said news staff at the SABC had been warned not to report on Malema's whereabouts or what he was doing.
News editors at the organisation were informed of the instruction earlier in the day, it said.
"Bemawu regards this as a gross violation of the principles of journalism and also an attack on freedom of the press," the union said in a statement.
"As a public broadcaster the SABC is duty bound to report news in a fair, unbiased and accurate manner, and without influence from top or any other management of the SABC."
Bemawu had informed its members not to comply with the unlawful instruction and to report the news of the day without fear or prejudice.
"If management dare to touch any of our members ignoring this unlawful instruction, Bemawu will defend our members and take the matter to the highest court."
The union called for an urgent investigation and demanded the strongest action be taken against the managers responsible for the instruction. – Sapa