National Union of Metalworkers of South Africa (Numsa) general secretary, Irvin Jim, on Sunday encouraged members of Cosatu to "quickly get out" and join their new rival labour federation.

The new federation aimed to attract 70% of the Congress of South African Trade Union (Cosatu) members and non-unionised workers, Irvin Jim said during a Workers’ Day celebration at Mehlareng Stadium in Tembisa, on the East Rand.

"We are building a new federation. The first priority we are targeting is 70% of workers who are not organised. Those workers must leave Cosatu in droves. Why must they have some sister who is president who has no clue what is the state of South African economy?" he said.

Cosatu is an alliance partner of the ANC.

Workers exploited under Cosatu

The National Union of Metalworkers of SA (Numsa) was expelled from Cosatu in November 2014 for not supporting the ANC in the elections that year.

Jim said workers were still being exploited under the Congress of SA Trade Unions (Cosatu).

"Numsa and many other unions here agreed that the path and vision that we championed is the right one. Some of them did not join the 'sweetheart' federation called Cosatu that is busy confusing workers next door," he said.

Cosatu was hosting its own May Day rally in Tshwane, where President Jacob Zuma was main speaker.

Jim said the new federation needed to meet government to defend workers’ rights and promised workers it would work tirelessly to defend its members.