Johannesburg - All Cosatu affiliates must accept the decision to expel Numsa, Cosatu deputy general secretary Bheki Ntshalintshali said on Tuesday.
"The decision to expel Numsa is a CEC decision and is binding on all the structures of the federation and its leaders," he told reporters in Johannesburg.
"All [are] expected to observe it without exception."
Ntshalintshali said the Congress of SA Trade Unions (Cosatu) would convene meetings at all of its structural levels to explain the central executive committee's (CEC) decision.
The National Union of Metalworkers of SA (Numsa) was expelled from Cosatu at a special CEC meeting which ran into the early hours of Saturday morning.
Numsa made a presentation to the meeting defending itself against charges that the had union contravened Cosatu's constitution.
The metalworkers' union was expelled by 33 votes to 24.
Ntshalintshali said Numsa was advised that it could appeal against its expulsion, to Cosatu's national congress.
The next national congress is expected to be held next year.
He said the decision to oust Numsa was not taken lightly.
Cosatu general secretary Zwelinzima Vavi was not present, with spokesperson Norman Mampane saying Vavi was "consulting his lawyers".