"The National Union of Metalworkers of South Africa is disgusted that Cosatu's Central Executive Committee has endorsed Deputy President Cyril Ramaphosa to take over as leader of the ANC and that it will be campaigning and lobbying to influence ANC structures to support its call", Numsa general secretary Irvin Jim said.
Numsa, which is the biggest union in the country, labelled Ramaphosa as enemy number one of the working class mainly for his business interests and his role as the government representative at the National Economic Development and Labour Council (Nedlac).
Kodwa said Zuma was invited to the December 2 meeting in his capacity as leader of the organisation to review the health and current state of the 104-year-old organisation.
In ANC tradition, the deputy usually ascends to the top post, but some in the party think Mr Ramaphosa would take the party too far from its left-wing roots.
While Cosatu said it backed Ramaphosa because of his strong union roots and contribution to the country's Constitution, Numsa believed the democratic Constitution ensured black people stayed out of the economy.
Worker federation Cosatu has announced its endorsement for deputy president Cyril Ramaphosa as the next president of the party. The leader of the party, which has a majority in parliament, will probably become president in a national vote in 2019.
Cosatu does not have voting power in the ANC, but boasts over a million members.
South Africa's President Jacob Zuma will challenge a report released this month by the anti-corruption watchdog.
Cosatu general secretary Bheki Ntshalintshali said it had "resolved to support and lobby" for Ramaphosa, a former anti-apartheid activist and trade unionist who helped negotiate the end of white-minority rule in 1994.
Zuma's popularity has waned due to a raft of recent scandals but he remains in favour among the ANC grassroots and can count on the backing of large sections of the party, including the youth and women's leagues.
Nkosazana Dlamini-Zuma, chairperson of the African Union Commission.
She indicated that she would be free to take up the position if required.
Detractors of the ruling party wanted to see regime change and did not support continued ANC rule in South Africa, Losi added.