Numsa is breaking ties with the tripartite alliance, its general secretary announced on Monday.
“We decided to break with the alliance and resolved to form a United Front and explore the possibility of socialism in South Africa,” Irvin Jim told reporters in Johannesburg.
The tripartite alliance consists of trade union federation Cosatu, the ruling African National Congress and the SA Communist Party.
The National Union of Metalworkers of SA said it would be launch the United Front before the end of the year.
“In December this year, 2014, we are launching the United Front,” said Jim.
The union, one of the biggest in the Congress of SA Trade Unions federation, announced in December 2013 it was exploring the possibility of forming a new political party. SAPA