The South African Transport and Allied Workers' Union (Satawu) fired its Gauteng provincial secretary Gift Ndawande after it was found he was an undocumented immigrant. According to Times Live, it was found that he has been living in South Africa illegally.
"The department said Ndwandwe was a Zimbabwean citizen who was in the country illegally and as such his employment was to be terminated."
Ndwandwe indicated he would take legal action against the department after he was arrested last week.
His appeal to his dismissal was unsuccessful and the union took a decision to relieve him of his duties with immediate effect on Wednesday.
According to IOL, Ndwandwe refused to be drawn into the matter, saying: "I don't have any comment on that matter."
"Last October Satawu received a letter from the department of home affairs instructing the union to terminate Gift Ndwandwe's employment because he was found to have fraudulently obtained his South African identity document," the union said in a statement.
Ndwandwe's ascension to the union's higher ranks was concluded amid much displeasure from some party members after he was elected as the union secretary in 2015 following the killing of former secretary Chris Nkosi.
The controversy surrounding his legality in the country emerged three months after the national union's general secretary Zenzo Mahlangu was deported to Zimbabwe.