The Congress of South African Trade Unions (Cosatu) has resolved that President Jacob Zuma will no longer be welcome to address its functions.
The union announced on Tuesday that the decision was made during a meeting.
Cosatu secretary-general Bheki Ntshalintshali said the ban “will be communicated to the ANC, including implications for the alliance”.
“We have agreed with the position of workers that allowing Zuma to address the May Day rally was not consistent with our position that we no longer trusted and supported Zuma’s leadership,” said Mr Ntshalintshali.
Earlier this month, President Zuma was booed at a Cosatu May Day rally in Bloemfontein.
His arrival at the Workers Day event was met with jeers and heckling, forcing the federation to cancel all scheduled speeches on the day.
Workers made it clear that the under-fire president was unwanted at the rally.
Cosatu president S’dumo Dlamini was also not spared the booing when he called for unity as well as the ANC national executive committee member, Ms Naledi Pandor, whose attempts to address workers failed.
The hostility shown to the president came after a request by three Cosatu affiliates that he be barred from addressing the rally.
The South African Democratic Teachers Union (SADTU), the National Health Education and Allied Workers Union (NEHAWU) and the Communication Workers Union (CWU) sent letters to Cosatu’s national office bearers a week before the May Day celebrations, protesting President Zuma’s invitation